Acute Pancreatitis
Acute inflammatory condition of the pancreas caused by premature activation of pancreatic enzymes, leading to autodigestion, edema, and potentially hemorrhagic necrosis of pancreatic tissue.
Acute pancreatitis is an acute inflammatory condition of the pancreatic parenchyma characterised by abdominal pain and elevated levels of pancreatic enzymes in the blood [1][2]. The name itself tells you the condition: "pan" = all, "creas" = flesh (Greek, referring to the fleshy organ), "-itis" = inflammation. So pancreatitis literally means "inflammation of the pancreas."
The key concept is autodigestion — the pancreas, which normally produces powerful digestive enzymes meant for the duodenum, begins digesting itself. This is what distinguishes pancreatitis from other causes of abdominal pain and makes it potentially lethal.
Core Concept
Acute pancreatitis = premature activation of pancreatic enzymes (especially trypsinogen → trypsin) within the pancreatic acinar cells → autodigestion → local and systemic inflammation. Everything else — the pain, the complications, the organ failure — flows from this single pathological event.
- Incidence: Approximately 13–45 per 100,000 population per year globally, with incidence rising over recent decades (likely due to increasing obesity, gallstone disease, and alcohol consumption).
- Age: Can occur at any age, but peak incidence is in the 4th–6th decades. Gallstone pancreatitis is more common in older adults (especially women), while alcoholic pancreatitis tends to present in younger men (30s–40s).
- Sex: Gallstone pancreatitis has a female predominance (mirrors gallstone epidemiology — "Fat, Forty, Female, Fertile, Fair"). Alcoholic pancreatitis has a male predominance.
- Hong Kong context: Gallstones are the leading cause. Alcohol is the second most common. Notably, Hong Kong has a relatively high prevalence of hepatobiliary disease including recurrent pyogenic cholangitis (RPC) related to Clonorchis sinensis (liver fluke) infection, which can also cause biliary pancreatitis. Post-ERCP pancreatitis is a recognized iatrogenic cause in tertiary centres performing high volumes of ERCP.
- Mortality:
- Overall mortality: ~2–5%
- Mild acute pancreatitis (interstitial/oedematous): < 1% mortality
- Severe acute pancreatitis (necrotising with organ failure): 15–40% mortality [1][3]
- Since the associated mortality of fulminant acute pancreatitis approaches 40%, early identification of high-risk patients and aggressive supportive care is critical [3].
The classic mnemonic for causes doubles as risk factors. Think "I GET SMASHED":
| Letter | Risk Factor |
|---|---|
| I | Idiopathic |
| G | Gallstones (55%) [4] |
| E | Ethanol / Chronic alcoholism (35%) [4] |
| T | Trauma (including iatrogenic, e.g. post-TOCE) [4] |
| S | Steroids / Surgery |
| M | Metabolic (hyperlipidaemia, hypercalcaemia) [4] |
| A | Autoimmune (SLE, Sjögren's, IgG4-related disease) |
| S | Scorpion stings (rare, but classic board fodder) |
| H | Hyperlipidaemia / Hypercalcaemia / Hypothermia |
| E | ERCP |
| D | Drug-induced (chemotherapy, anticonvulsants) [4] |
Risk factors for severe disease (important for prognosis):
- Age > 55
- Obesity (BMI > 30) — predisposes to peripancreatic fat necrosis
- Organ failure at presentation
- Pleural effusion or pulmonary infiltrates
- APACHE II score ≥ 8 at admission [3]
- CRP > 150 mg/L at 48 hours [2]
4. Anatomy and Function of the Pancreas
Understanding the anatomy is essential because it explains why pancreatitis causes the clinical features it does (retroperitoneal pain, vascular complications, splenic vein thrombosis, etc.).
The pancreas is a retroperitoneal organ lying obliquely across the posterior abdominal wall, with the tail higher than the head [3].
Four sections (right to left):
| Section | Anatomical Relations | Clinical Relevance |
|---|---|---|
| Head / Uncinate | Cradled by the C-loop of the duodenum; uncinate process hooks behind the superior mesenteric vessels | Tumours here → obstructive jaundice; oedema of head → bile duct compression |
| Neck | Lies anterior to the mesenteric vessels and portal vein | Inflammation here → portal/SMV thrombosis |
| Body | Begins at the left border of the SMV; lies anterior to the aorta, left renal vein, and left adrenal gland | Retroperitoneal inflammation explains back pain |
| Tail | Sits close to the splenic hilum, anterior to the left adrenal gland | Tail inflammation → splenic vein thrombosis → left-sided (sinistral) portal hypertension |
- Main pancreatic duct (duct of Wirsung): Runs the length of the pancreas, joins the common bile duct (CBD) at the ampulla of Vater (hepatopancreatic ampulla), which opens into the second part of the duodenum at the major duodenal papilla.
- Accessory pancreatic duct (duct of Santorini): Drains the upper head; opens at the minor duodenal papilla.
- The sphincter of Oddi controls flow of bile and pancreatic juice into the duodenum. This is clinically important because:
- A gallstone impacting at the ampulla obstructs both the CBD and the pancreatic duct → reflux of bile into the pancreatic duct → pancreatitis.
- Drugs like morphine cause sphincter of Oddi spasm → theoretically worsening obstruction.
Acute biliary pancreatitis occurs when a gallstone (particularly small stones from a gallbladder with multiple small stones) passes through a wide cystic duct and impacts at the common channel (the shared terminal portion of the CBD and pancreatic duct at the ampulla) [5]. The stone obstructs outflow → bile reflux into the pancreatic duct → enzyme activation → pancreatitis.
Arterial supply: Dual supply from the coeliac trunk and the superior mesenteric artery (SMA) [3]:
- Head: Superior pancreaticoduodenal arteries (from gastroduodenal artery, a branch of the coeliac trunk) and inferior pancreaticoduodenal arteries (from the SMA) — these form anastomotic arcades around the head.
- Body and Tail: Branches of the splenic artery (dorsal pancreatic, great pancreatic/pancreatica magna, caudal pancreatic arteries).
Venous drainage [3]:
- Superior and inferior pancreaticoduodenal veins → SMV
- Splenic veins → portal vein
- This is why pancreatitis can cause splenic vein thrombosis (the vein runs along the posterior surface of the pancreas) and portal vein thrombosis.
| Function | Cells | Products | Clinical Significance |
|---|---|---|---|
| Exocrine (98% of pancreas) | Acinar cells | Digestive enzymes: trypsinogen, chymotrypsinogen, proelastase, lipase, amylase, phospholipase A2 | Premature activation → autodigestion |
| Exocrine | Ductal cells | Bicarbonate-rich alkaline fluid | Neutralises gastric acid in duodenum |
| Endocrine (2% — islets of Langerhans) | β-cells, α-cells, δ-cells | Insulin, glucagon, somatostatin | Destruction → hyperglycaemia / diabetes |
Normal protective mechanisms against autodigestion:
- Enzymes are synthesised as inactive zymogens (e.g., trypsinogen, not trypsin)
- Stored in zymogen granules — physically separated from cytoplasm
- Pancreatic secretory trypsin inhibitor (PSTI/SPINK1) — a "safety catch" that inhibits any prematurely activated trypsin
- Enzymes are only activated in the duodenal lumen by enterokinase (which converts trypsinogen → trypsin, and trypsin then activates all other zymogens in a cascade)
Pancreatitis occurs when these protective mechanisms fail.
5. Aetiology
The two dominant causes account for ~90% of cases:
A useful mnemonic specifically from senior notes: GAME ID [2]:
- G = Gallstone (most common): suspect if history of biliary colic or ↑ALP
- A = Alcohol: suspect if ↑AST
- M = Metabolic: hypertriglyceridaemia / hypercalcaemia
- E = ERCP: reduced by PR NSAID or temporary pancreatic stenting
- I = Idiopathic (10%)
- D = Drugs (NSAIDs, steroids, azathioprine, ACEi, valproate)
5.2 Detailed Aetiology with Pathophysiological Mechanisms
Mechanism: A gallstone (usually small, < 5 mm) migrates from the gallbladder through the cystic duct and impacts at the ampulla of Vater [3][5]:
- Transient or persistent obstruction of the common channel → reflux of bile into the pancreatic duct (the "common channel theory")
- Bile activates trypsinogen to trypsin within the pancreatic parenchyma
- Trypsin triggers a cascade of activation of other zymogens → autodigestion
- Additionally, obstruction causes increased intraductal pressure → acinar cell injury
Clinical clues: History of biliary colic, female sex, ↑ALP and bilirubin (cholestatic pattern), gallstones visible on USG.
The slide shows that biliary pancreatitis is facilitated by: wide cystic duct, multiple small stones, a common channel larger than the size of the stone [5]. This means small stones can easily traverse the cystic duct but then impact at the narrower ampulla.
Why Small Stones Are Dangerous
Counterintuitively, small gallstones (< 5 mm) are more dangerous for pancreatitis than large ones. Large stones get stuck in the cystic duct (causing cholecystitis), but small stones slip through and impact at the ampulla (causing pancreatitis). This is why patients with microlithiasis or biliary sludge are at particular risk.
Mechanism [3]:
- Alcohol increases synthesis of digestive enzymes AND lysosomal enzymes (cathepsin B) by pancreatic acinar cells
- Cathepsin B can convert trypsinogen → trypsin within the acinar cell (co-localisation hypothesis)
- Alcohol also causes protein plug formation in small pancreatic ductules → obstruction
- Alcohol is directly toxic to acinar cells, causing oxidative stress and mitochondrial dysfunction
- Usually requires chronic heavy intake (> 4–5 drinks/day for > 5 years), but acute binge can precipitate an acute episode
Clinical clues: History of chronic heavy alcohol use, ↑AST (AST:ALT > 2 is suggestive of alcohol), hepatomegaly, stigmata of chronic liver disease.
Hypertriglyceridaemia (TG > 11.3 mmol/L or > 1000 mg/dL):
- Lipase is thought to liberate toxic fatty acids into the pancreatic microcirculation → microcirculatory impairment and ischaemia → acinar cell injury [3]
- The free fatty acids are directly cytotoxic to acinar cells and capillary endothelium
- Commonly seen in familial hyperlipoproteinaemia (Types I, IV, V), uncontrolled diabetes, pregnancy, alcohol use, certain drugs (oestrogens, tamoxifen, protease inhibitors)
Hypercalcaemia (most commonly from hyperparathyroidism):
- Definition: abdominal pain + increase in serum amylase > 3x ULN + requires hospitalisation [6]
- Pathogenesis: activation of acinar cells by mechanical, chemical or hydrostatic injury during the procedure [6]
- Occurs in approximately 4% of ERCP procedures [6]
- Risk factors [6]:
- Patient factors: young female, suspected sphincter of Oddi dysfunction, history of post-ERCP pancreatitis, recurrent pancreatitis
- Procedural factors: pre-cut sphincterotomy, pancreatic duct injection
- Prevention [6]:
- Pharmacological: PR NSAID (e.g. indomethacin) pre-operatively
- Mechanical: pancreatic duct stent, guidewire cannulation before contrast injection (by avoiding injection into the pancreatic duct)
Mnemonic: "SAND-TV" — Steroids, Azathioprine, NSAIDs, Diuretics (furosemide/thiazides), Trimethoprim-sulfamethoxazole, Valproic acid
- Dipeptidyl peptidase-4 (DPP-4) inhibitors (e.g. sitagliptin — used in diabetes)
- Chemotherapy, anticonvulsants [4]
- ACE inhibitors [2]
Mechanism varies by drug: direct toxic effect on acinar cells, immunological reaction, increased viscosity of pancreatic juice, or sphincter of Oddi spasm.
| Category | Organisms |
|---|---|
| Bacteria | Mycoplasma, Legionella, Leptospira |
| Viruses | Mumps, Coxsackievirus B, HBV, EBV, CMV, VZV, HSV, HIV |
| Fungi | Aspergillus |
| Parasites | Ascaris lumbricoides, Clonorchis sinensis (relevant in HK), Toxoplasma, Cryptosporidium |
Clonorchis sinensis is particularly relevant in Hong Kong — these liver flukes reside in the bile ducts and can cause biliary obstruction → pancreatitis. This overlaps with the aetiology of recurrent pyogenic cholangitis (RPC) [7].
- Pancreatic tumours: Can obstruct the main pancreatic duct
- Periampullary tumours: Obstruct the ampulla (ampullary adenoma/carcinoma, cholangiocarcinoma, duodenal carcinoma)
- Always consider in older patients with "idiopathic" first episode of pancreatitis — do cross-sectional imaging!
- Autoimmune pancreatitis (AIP): IgG4-related disease (Type 1) or duct-centric pancreatitis (Type 2)
- SLE, Sjögren's syndrome, Primary biliary cholangitis (PBC)
- Mechanism: immune-mediated ductal and acinar inflammation
- Pancreas divisum: Most common congenital anomaly of the pancreas [2] — failure of fusion of the dorsal and ventral pancreatic buds → the majority of the pancreas drains through the minor papilla (which may be inadequate → recurrent pancreatitis)
- Annular pancreas, choledochal cysts
- Pregnancy (related to gallstones and hypertriglyceridaemia)
- Scorpion venom (exotic but board-classic — stimulates pancreatic secretion)
6. Pathophysiology
This is the heart of understanding the disease. Everything — the clinical features, the complications, the management — makes sense once you understand the pathophysiology.
Activation of pancreatic enzymes → Autodigestion of pancreas → Pancreatic necrosis [8]
Step by step:
- Initiating insult (gallstone obstruction, alcohol toxicity, etc.) → disruption of normal protective mechanisms
- Unregulated premature activation of pancreatic enzymes, especially trypsin, within pancreatic acinar cells [3]
- Trypsin activates a cascade of other zymogens:
- Elastase → digests blood vessel walls → haemorrhage
- Phospholipase A2 → digests cell membranes → cell death
- Lipase → digests peripancreatic fat → fat necrosis (the chalky white spots you see at surgery)
- Autodigestion of pancreatic tissues → peripancreatic and pancreatic necrosis [3]
- Autodigestion extends beyond the pancreas into the retroperitoneum, digesting peripancreatic tissues, causing fat necrosis and erosion of blood vessels with haemorrhage [3]
- Entry of enzymes into the bloodstream may cause respiratory and renal injury and other systemic effects [3]
NF-κB-dependent inflammatory pathway regulates the synthesis of multiple cytokines and chemokines → recruitment of inflammatory cells (neutrophils, macrophages) → these magnify and propagate systemic inflammation [3].
Key mediators:
- Pro-inflammatory cytokines: TNF-α, IL-1, IL-2, IL-6 [3]
- Chemokines and anti-inflammatory factors
- Inflammatory cells, once recruited to the pancreas, cause further acinar cell injury → a vicious cycle [3]
This cytokine storm is what converts a local pancreatic problem into a systemic disease (SIRS → MODS).
This is a critical teaching point from the lecture slides:
Acute oedematous pancreatitis → Volume depletion → Hypoperfusion of gut and pancreas → Mucosal barrier breakdown → Pancreatic necrosis + Peripancreatic necrosis → Endotoxaemia [9]
Reasons for progression [10]:
- Hypoperfusion of pancreas — as the inflammatory oedema and third-spacing cause volume depletion, the pancreas itself becomes ischaemic, converting potentially reversible oedematous pancreatitis into irreversible necrosis
- Persistent ampullary obstruction by stone — ongoing obstruction prevents resolution and drives continued enzyme activation
Also from the slides, the parallel pathway [8]:
Activation of pancreatic enzymes → Autodigestion of pancreas → Pancreatic necrosis (direct enzyme damage pathway)
AND simultaneously:
Occlusion of blood vessels within the pancreas → Hypoperfusion of pancreas → additional ischaemic necrosis [8]
Enzyme leakage into retroperitoneum → Peripancreatic necrosis [8]
Why Aggressive Fluid Resuscitation Matters
The progression from oedematous to necrotising pancreatitis is driven by hypovolaemia → pancreatic hypoperfusion. This is why early aggressive IV fluid resuscitation (goal-directed, typically Lactated Ringer's at 5–10 mL/kg/hr initially) is the cornerstone of management — you are trying to maintain pancreatic perfusion and prevent necrosis.
When the gut becomes hypoperfused, the intestinal mucosal barrier breaks down → bacterial translocation (gut bacteria, especially Gram-negatives like E. coli, Klebsiella, enter the bloodstream and reach the necrotic pancreas) → infected pancreatic necrosis → sepsis. This is the main mechanism by which sterile necrosis converts to infected necrosis, and it is the leading cause of late mortality in severe acute pancreatitis.
7. Classification
Two broad categories based on whether necrosis is present [2]:
| Type | Features | Proportion | Prognosis |
|---|---|---|---|
| Interstitial oedematous pancreatitis | Diffuse or focal enlargement of pancreas with homogeneous enhancement on CT; no necrosis | ~80% | Usually self-limiting; < 1% mortality |
| Necrotising pancreatitis | Areas of non-enhancement on contrast CT (= necrosis); can be pancreatic, peripancreatic, or both | ~20% | 15–40% mortality (higher if infected) |
This is the most important classification for clinical practice and exams:
| Severity | Definition | Mortality |
|---|---|---|
| Mild | NO organ failure and NO local or systemic complications | < 1% |
| Moderately severe | Transient organ failure resolving within 48 hours, OR local/systemic complications without persistent organ failure | ~2–5% |
| Severe | Persistent organ failure > 48 hours (involving one or multiple organs) | 15–40% |
Organ failure is defined using the Modified Marshall Scoring System for three organ systems:
- Respiratory: PaO₂/FiO₂ ≤ 300 (= acute lung injury/ARDS)
- Cardiovascular: Systolic BP < 90 mmHg not responsive to fluid resuscitation (= shock)
- Renal: Creatinine ≥ 170 μmol/L (= acute kidney injury)
A score of ≥ 2 in any system = organ failure.
Key Exam Point
Don't confuse the old "mild vs severe" binary classification with the updated Revised Atlanta 3-tier classification. The moderately severe category was added because many patients have local complications (e.g. pseudocyst) or transient organ failure but recover — lumping them with those who have persistent multi-organ failure overstates their risk.
7.3 Scoring Systems for Severity Prediction
Mnemonic: 0 hours = "GALAW", 48 hours = "CHOBBS" [2]
At admission (0 hours) — GALAW:
| Parameter | Cut-off |
|---|---|
| Glucose | > 11.1 mmol/L |
| Age | > 55 years |
| LDH | > 350 U/L |
| AST | > 250 U/L |
| WBC | > 16 × 10⁹/L |
At 48 hours — CHOBBS:
| Parameter | Cut-off |
|---|---|
| Ca²⁺ | < 2 mmol/L (8 mg/dL) |
| Hematocrit | Fall by ≥ 10% |
| Oxygen (PaO₂) | < 8 kPa (60 mmHg) |
| Base deficit | > 4 mEq/L |
| BUN | ↑ by ≥ 1.8 mmol/L (5 mg/dL) despite fluids |
| Sequestration of fluid | > 6000 mL |
Interpretation [3]:
- Score < 3: Mortality 0–3% (mild)
- Score ≥ 3: Mortality 11–15% (severe if score ≥ 3) [2]
- Score ≥ 6: Mortality ~40%
Limitation: Cannot be fully calculated until 48 hours after admission [3]. Validated for alcoholic/gallstone pancreatitis only [2].
- 14 parameters: Age, rectal temperature, MAP, HR, RR, GCS, A-a gradient or PaO₂, pH or HCO₃, haematocrit, WBC, serum Na⁺, serum K⁺, creatinine, chronic disease points [3]
- Advantage: Can be calculated at admission and updated daily to allow continual reassessment [3]
- Disadvantage: Somewhat cumbersome and difficult to calculate, which limits its everyday use [3]
- Interpretation [3]:
- Score < 8: Mortality < 4%
- Score ≥ 8: Mortality 11–18% (indicates severe acute pancreatitis) [2]
- ≥ 3 out of 8 parameters in the first 48 hours indicates severe attack [2]
- Parameters (mnemonic "PANCREAS"): PaO₂ < 8 kPa, Age > 55, Neutrophils (WBC) > 15 × 10⁹/L, Calcium < 2 mmol/L, Renal (urea > 16 mmol/L), Enzymes (LDH > 600 U/L), Albumin < 32 g/L, Sugar (glucose > 10 mmol/L)
- Grade of pancreatitis (0–4) + percentage of necrosis (0–6) [2]
- Used to correlate CT findings with prognosis
- Higher scores predict morbidity and mortality
- Simple, widely available biomarker
- Predicts severe attack [2]
- 5 parameters (within 24 hours): BUN > 25 mg/dL, Impaired mental status, SIRS, Age > 60, Pleural effusion
- Score ≥ 3: significantly increased mortality
- Advantage: Can be calculated within 24 hours (faster than Ranson's)
Scoring Systems — What to Remember for Exams
Ranson's criteria — the one to memorize in detail (GALAW + CHOBBS). Know that it requires 48 hours to complete and ≥ 3 = severe. APACHE II — calculated at admission and daily; ≥ 8 = severe. Glasgow — ≥ 3/8 in first 48h = severe. CRP > 150 at 48h — simple predictor of severity. BISAP — quick bedside score within 24h.
8. Clinical Features
| Symptom | Mechanism / Pathophysiological Basis |
|---|---|
| Upper abdominal pain with radiation to back [11] | The pancreas is retroperitoneal — inflammation irritates the retroperitoneal nerves (coeliac plexus), which refer pain to the back (T6–T10 dermatomes). Pain is epigastric because the pancreas lies in the epigastrium. |
| Severe, constant pain | Unlike biliary colic (which waxes and wanes), pancreatic pain is constant because ongoing autodigestion causes sustained tissue inflammation. Persists for several hours to days [3]. |
| Rapid onset (gallstones) vs less abrupt (alcohol) [3] | Gallstone impaction causes sudden obstruction → sudden enzyme activation. Alcohol causes gradual toxic insult → more insidious onset. |
| Relieved by sitting up or leaning forward [3] | Leaning forward takes tension off the retroperitoneum and the coeliac plexus. Lying supine causes the inflamed pancreas to press against the vertebral column, worsening pain. This is a classic clinical pearl. |
| Nausea and vomiting [3][11] | (1) Visceral afferent stimulation from pancreatic inflammation triggers the vomiting centre. (2) Paralytic ileus from retroperitoneal inflammation reduces gut motility → nausea. (3) Vomiting is often persistent and does not relieve the pain (unlike peptic ulcer where vomiting may relieve). |
| Fever [11] | Chemical/sterile inflammation triggers the cytokine cascade (TNF-α, IL-1, IL-6 → hypothalamic set point ↑). Note: fever in acute pancreatitis is initially "chemical" (i.e. from inflammation, not infection) [2]. Infected necrosis should be suspected if fever persists beyond 7–10 days or recurs. |
| Dyspnoea [3] | Three mechanisms: (1) Diaphragmatic inflammation from adjacent pancreatic inflammation, (2) Pleural effusions (typically left-sided — due to transdiaphragmatic lymphatic drainage of enzyme-rich exudative fluid), (3) ARDS in severe cases (from systemic cytokine storm → pulmonary capillary leak). |
| Tetany [2] | Transient hypocalcaemia due to fat saponification — pancreatic lipase causes fat necrosis → released fatty acids bind (precipitate with) calcium → hypocalcaemia → neuromuscular excitability → tetany [2]. Also, hypoalbuminaemia (from third-spacing) reduces total calcium. |
8.2 Signs
| Sign | Mechanism |
|---|---|
| Xanthoma and xanthelasma | Clue to hypertriglyceridaemia as the underlying cause [3] |
| Jaundice | Obstructive jaundice due to choledocholithiasis (gallstone in CBD) OR oedema of the head of pancreas compressing the intrapancreatic portion of the CBD [3] |
| Tachycardia [11] | Hypovolaemia from massive third-spacing of fluid into the retroperitoneum and peritoneal cavity + pain + systemic inflammatory response |
| Tachypnoea | Compensation for metabolic acidosis (base deficit), pain, or respiratory compromise (pleural effusion/ARDS) [3] |
| Hypoxaemia | ARDS, pleural effusions, atelectasis from diaphragmatic splinting [3] |
| Hypotension | Massive fluid third-spacing (up to > 6 L in severe cases — hence "sequestration of fluid > 6000 mL" in Ranson's criteria), vasodilation from SIRS, and haemorrhage if vessel erosion occurs [3] |
Inspection:
| Sign | Description | Mechanism |
|---|---|---|
| Abdominal distension | Generalised distension [3] | Paralytic ileus (retroperitoneal inflammation → reflex inhibition of gut motility) and/or ascites (enzyme-rich fluid leaking into the peritoneal cavity) |
| Cullen's sign | Ecchymotic discolouration in the periumbilical region [2][3][11] | Retroperitoneal haemorrhage tracking along the falciform ligament to the umbilicus. Indicates haemorrhagic/necrotising pancreatitis — a sign of severity. |
| Grey Turner's sign | Ecchymotic discolouration along the flank [2][3][11] | Retroperitoneal haemorrhage tracking laterally to the flanks. Same implication as Cullen's sign. |
| Fox's sign | Ecchymotic discolouration over the inguinal ligament [2] | Retroperitoneal haemorrhage tracking to the groin. Less commonly tested but mentioned in notes. |
| Pancreatic panniculitis [3] | Tender red/violaceous subcutaneous nodules, frequently on distal extremities | Circulating pancreatic lipase causes subcutaneous fat necrosis. Rare but pathognomonic. |
Cullen's and Grey Turner's Signs
These signs are LATE findings — they take 24–48 hours to develop. Their presence indicates haemorrhagic/necrotising pancreatitis and carries a poor prognosis. They are NOT specific to pancreatitis — any cause of retroperitoneal haemorrhage (e.g. ruptured AAA) can produce them.
Palpation:
| Sign | Mechanism |
|---|---|
| Epigastric tenderness [3] | Direct inflammation of the pancreas in the epigastrium |
| Guarding (but often surprisingly less than expected) | The pancreas is retroperitoneal, so peritoneal signs may be less prominent than in hollow viscus perforation. However, if enzyme-rich fluid spills into the peritoneal cavity, you get chemical peritonitis with generalised guarding. |
| Hepatosplenomegaly [3] | Seen in alcoholic pancreatitis — coexisting alcoholic liver disease causes hepatomegaly; portal hypertension from splenic vein thrombosis or alcoholic cirrhosis causes splenomegaly. |
| Palpable epigastric mass | Late sign — suggests pseudocyst formation (> 4 weeks after onset) |
Percussion:
| Sign | Mechanism |
|---|---|
| Shifting dullness | Pancreatic ascites — enzyme-rich fluid leaking through disrupted pancreatic duct or from peripancreatic inflammation into the peritoneal cavity |
Auscultation:
| Sign | Mechanism |
|---|---|
| Hypoactive/absent bowel sounds [3] | Paralytic (adynamic) ileus — retroperitoneal inflammation causes reflex inhibition of peristalsis via the splanchnic nerves |
| Decreased breath sounds at left base | Left-sided pleural effusion (more common than right due to anatomical proximity of pancreatic tail to left hemidiaphragm) |
These should trigger escalation of care:
- Cullen's / Grey Turner's / Fox's signs (retroperitoneal haemorrhage)
- Tachycardia with hypotension (shock)
- Oliguria (AKI)
- Confusion/altered mental status (encephalopathy from hypoxia/hypotension/metabolic derangement)
- Respiratory distress (ARDS)
- Abdominal compartment syndrome (tense distension, oliguria, respiratory failure — from massive retroperitoneal oedema)
9. Clinical Approach to a Patient with Suspected Acute Pancreatitis
A structured approach on the ward:
- Epigastric pain radiating to back, worse lying flat, better leaning forward, with nausea/vomiting → think pancreatitis
- High level of clinical suspicion [11] — the slide emphasises this
- History: alcohol, gallstones, recent ERCP, drugs, family history of hyperlipidaemia
- Investigations: LFT pattern (cholestatic = biliary), lipid panel, calcium, USG for gallstones
- Ranson's, APACHE II, Glasgow, BISAP scores
- CRP at 48 hours
- CT abdomen with contrast (ideally at 72–96 hours for necrosis assessment)
- Look for organ failure (Modified Marshall Score)
- (To be covered in detail in the next response)
| Pathophysiological Event | Clinical Feature |
|---|---|
| Retroperitoneal inflammation | Epigastric pain radiating to back; relieved by leaning forward |
| Autodigestion by lipase → fat necrosis → Ca²⁺ saponification | Hypocalcaemia → tetany |
| Elastase digesting blood vessels → retroperitoneal haemorrhage | Cullen's, Grey Turner's, Fox's signs |
| Cytokine storm (SIRS) | Fever, tachycardia, tachypnoea, hypotension, organ failure |
| Third-spacing of fluid (> 6 L) | Hypovolaemia → shock, haemoconcentration (↑ Hct), prerenal AKI |
| Paralytic ileus (reflex from retroperitoneal inflammation) | Abdominal distension, hypoactive bowel sounds, vomiting |
| Transdiaphragmatic inflammation/lymphatic drainage | Left pleural effusion, diaphragmatic splinting → dyspnoea |
| Pulmonary capillary leak from cytokines | ARDS |
| Islet cell destruction | Hyperglycaemia |
| Subcutaneous fat necrosis by circulating lipase | Pancreatic panniculitis |
| Bile duct obstruction (stone or oedema of head) | Jaundice |
High Yield Summary
Definition: Acute inflammation of pancreatic parenchyma from premature intracellular activation of trypsinogen → autodigestion.
Aetiology: Gallstones (55%) > Alcohol (35%) > Miscellaneous (10%) — GAME ID mnemonic.
Pathophysiology: Enzyme activation → autodigestion → pancreatic/peripancreatic necrosis → cytokine storm (NF-κB, TNF-α, IL-6) → SIRS → organ failure. Volume depletion → pancreatic hypoperfusion → progression to necrotising pancreatitis.
Classification (Revised Atlanta):
- Morphology: Interstitial oedematous vs. Necrotising
- Severity: Mild (no organ failure) → Moderately severe (transient OF < 48h or local complications) → Severe (persistent OF > 48h)
Scoring: Ranson's (GALAW + CHOBBS, ≥ 3 = severe, needs 48h), APACHE II (≥ 8 = severe, can calculate daily), Glasgow (≥ 3/8), CRP > 150 at 48h, BISAP.
Clinical features: Epigastric pain radiating to back (retroperitoneal), relieved by leaning forward, N/V, fever. Signs: Cullen's (periumbilical ecchymosis), Grey Turner's (flank ecchymosis), Fox's (inguinal ecchymosis) = haemorrhagic pancreatitis. Tetany from hypocalcaemia (fat saponification).
Diagnosis: 2/3 of — (1) Typical pain, (2) Amylase/lipase ≥ 3× ULN, (3) Imaging findings.
Active Recall - Acute Pancreatitis (Definition, Epidemiology, Aetiology, Pathophysiology, Classification, Clinical Features)
[1] General medical knowledge on acute pancreatitis (standard textbook) [2] Senior notes: maxim.md (Acute pancreatitis section) [3] Senior notes: felixlai.md (Acute pancreatitis section) [4] Lecture slides: Acute pancreatitis.pdf (p3 — Aetiology of acute pancreatitis) [5] Lecture slides: Acute pancreatitis.pdf (p4 — Acute biliary pancreatitis) [6] Senior notes: maxim.md (Post-ERCP pancreatitis section) [7] Senior notes: maxim.md (Gallstone pathology section) [8] Lecture slides: Acute pancreatitis.pdf (p5 — Activation of pancreatic enzymes pathway) [9] Lecture slides: Acute pancreatitis.pdf (p6 — Acute oedematous pancreatitis progression) [10] Lecture slides: Acute pancreatitis.pdf (p7 — Reasons for progression to necrotising pancreatitis) [11] Lecture slides: Acute pancreatitis.pdf (p8 — Diagnosis of acute pancreatitis clinical features)
Differential Diagnosis of Acute Pancreatitis
The differential diagnosis of acute pancreatitis is essentially the differential of severe acute epigastric pain — and it's a critical list because misdiagnosis can be fatal. The reason the DDx is broad is that the epigastrium is a "crossroads" — it overlays the stomach, duodenum, pancreas, biliary tree, transverse colon, aorta, and even receives referred pain from the heart and lungs. You need a high level of clinical suspicion [11] and must systematically exclude dangerous mimics.
The approach to the DDx should be organ-system-based, thinking about what structures lie in the epigastrium and upper abdomen, plus any extra-abdominal causes that can refer pain there.
Detailed Differential Diagnosis
The conditions listed below are taken from the senior notes [3][2] and supplemented with additional important mimics. For each, I explain why it mimics pancreatitis and the key distinguishing features.
- Why it mimics pancreatitis: Epigastric pain, nausea, vomiting. A posterior duodenal ulcer can even penetrate into the pancreas itself, causing a secondary pancreatitis and elevated amylase.
- Key distinguishing features:
- PUD pain classically has a relationship with food (gastric ulcer = worsened by eating; duodenal ulcer = relieved by eating, worse on empty stomach — "hunger pain")
- PUD pain is typically burning and more superficial; pancreatitis pain is deep, boring, and radiates to the back
- No significant elevation of amylase/lipase to ≥ 3× ULN in uncomplicated PUD
- Endoscopy (OGD) is diagnostic for PUD
- Why it mimics pancreatitis: Sudden severe epigastric pain. Perforated duodenal ulcer fluid can track down the right paracolic gutter and even irritate the pancreas, causing secondary hyperamylasaemia.
- PPU is a key DDx because serum amylase can be elevated (false positive for pancreatitis) [2] — gastric/duodenal contents leaking into the peritoneum contain salivary amylase, and peritoneal irritation causes amylase reabsorption.
- Key distinguishing features:
- PPU causes sudden onset "thunderclap" pain (the moment of perforation), whereas pancreatitis builds up over hours
- Board-like rigidity and generalised peritonism — PPU causes chemical peritonitis from free gastric acid. In pancreatitis (retroperitoneal), peritoneal signs are often less marked initially.
- CXR shows free air under the diaphragm (pneumoperitoneum) — this is absent in pancreatitis [2]
- Valentino's sign: gastric contents from a PPU can track down to the RLQ, mimicking appendicitis [6]
- CT abdomen with contrast is indicated when the diagnosis is uncertain (DDx PPU, gangrenous cholecystitis, ischaemic bowel) [2]
PPU vs Pancreatitis — The Amylase Trap
Elevated serum amylase does NOT automatically mean pancreatitis. PPU, ruptured AAA, DKA, bowel ischaemia, and macroamylasaemia can all cause a raised amylase. Always check a CXR for pneumoperitoneum (erect or lateral decubitus) before committing to a diagnosis of pancreatitis. Serum lipase is more specific for pancreatitis.
- Why it mimics pancreatitis: RUQ/epigastric pain, jaundice, deranged LFTs. In fact, gallstone pancreatitis and cholangitis frequently coexist — a stone at the ampulla can cause both simultaneously.
- Key distinguishing features:
- Charcot's triad (fever + abdominal pain + jaundice) or Reynolds' pentad (+ hypotension + confusion) points towards cholangitis [12]
- Cholangitis presents with a predominantly cholestatic LFT pattern (↑ALP, ↑GGT, ↑conjugated bilirubin) with less dramatic transaminase rise
- In pancreatitis, amylase/lipase ≥ 3× ULN is the hallmark; in cholangitis, amylase may be mildly elevated but usually < 3× ULN unless there is concurrent pancreatitis
- USG shows dilated CBD (> 6 mm, or > 10 mm post-cholecystectomy) with possible stone visible
- Important: if both cholangitis and pancreatitis are present (gallstone pancreatitis with cholangitis), ERCP within 24–72 hours is indicated [2]
- Why it mimics pancreatitis: RUQ pain (which can radiate to the epigastrium), fever, nausea/vomiting, leukocytosis, and even mildly elevated amylase.
- Key distinguishing features:
- Pain is predominantly RUQ, not epigastric. Positive Murphy's sign (inspiratory arrest on palpation of RUQ) — this sign is absent in pancreatitis
- Biliary colic (gallbladder contraction against an impacted stone) lasts < 6 hours and resolves; cholecystitis pain persists > 6 hours with systemic inflammation [12]
- USG shows gallbladder wall thickening (> 3 mm), pericholecystic fluid, distended gallbladder, and positive sonographic Murphy's sign
- Amylase/lipase are usually normal or only mildly elevated in isolated cholecystitis
- Why it mimics pancreatitis: Epigastric / RUQ pain, nausea, vomiting, jaundice, malaise. Acute viral hepatitis (especially HAV/HBV/HEV) can present with significant abdominal pain.
- Key distinguishing features:
- Hepatocellular LFT pattern: massively elevated transaminases (ALT/AST often > 1000 U/L) with bilirubin rise; in pancreatitis, transaminases are only mildly elevated (in gallstone pancreatitis ALT may rise to a few hundred, but not thousands)
- Viral serology (HBsAg, anti-HAV IgM, anti-HEV IgM) is diagnostic
- Amylase/lipase are normal in hepatitis
- Prodromal symptoms (fever, arthralgia, rash in HBV) may precede jaundice
- Why it mimics pancreatitis: Severe epigastric/periumbilical pain, often out of proportion to physical findings (classically "pain out of proportion to exam"), nausea, vomiting, and can cause elevated amylase (from ischaemic bowel releasing amylase).
- Key distinguishing features:
- Mesenteric ischaemia classically occurs in elderly patients with atrial fibrillation (embolic) or atherosclerotic risk factors (thrombotic), or post-prandially ("intestinal angina" in chronic mesenteric ischaemia)
- Pain out of proportion to physical examination is the hallmark — the abdomen is initially soft with minimal tenderness despite agonising pain. In pancreatitis, there is usually epigastric tenderness on examination.
- Metabolic (lactic) acidosis develops early
- CT angiography shows mesenteric vessel occlusion or bowel wall changes (pneumatosis, portal venous gas)
- CT abdomen with contrast is indicated when the diagnosis is uncertain (DDx PPU, gangrenous cholecystitis, ischaemic bowel) [2]
Mesenteric Ischaemia — The Silent Killer
This is one of the most dangerous misdiagnoses. If you have an elderly AF patient with severe abdominal pain and a relatively benign abdominal exam, think mesenteric ischaemia FIRST. Don't anchor on "probably pancreatitis" just because the amylase is a bit raised — ischaemic bowel also raises amylase.
- Why it mimics pancreatitis: Abdominal pain, vomiting, distension. Small bowel obstruction can cause a mildly elevated amylase (from mucosal ischaemia and reabsorption).
- Key distinguishing features:
- Pain in obstruction is classically colicky (comes and goes in waves) — pancreatitis pain is constant
- Absolute constipation (no flatus, no stool) in complete obstruction — not a feature of pancreatitis
- High-pitched, tinkling bowel sounds in mechanical obstruction vs hypoactive/absent bowel sounds in pancreatitis (paralytic ileus)
- AXR shows dilated bowel loops with air-fluid levels in a stepladder pattern; in pancreatitis, you see sentinel loop sign and colonic cut-off sign instead [2]
This is the one you must not miss. It was specifically highlighted with an asterisk in the senior notes [3].
- Why it mimics pancreatitis: An inferior MI can present as epigastric pain, nausea, and vomiting — because the inferior surface of the heart (supplied by the RCA) sits on the diaphragm, referring pain to the epigastrium via shared T5–T9 visceral afferents.
- Key distinguishing features:
- Risk factors for coronary artery disease (smoking, diabetes, hypertension, hyperlipidaemia, family history)
- Pain is more commonly described as crushing, pressure-like, with radiation to the left arm, jaw, or neck — though atypical presentations (especially in diabetics, elderly, women) may lack these classic features
- ECG changes (ST elevation/depression, new LBBB, pathological Q waves)
- Cardiac markers (troponin TnI/TnT) are elevated — this is exactly why troponin ± ECG is part of the workup for acute pancreatitis, to exclude MI as a differential [3]
- Amylase/lipase are normal in MI (unless there is concurrent mesenteric ischaemia from cardiogenic shock)
Cardiac markers ± ECG should be checked in every patient presenting with acute epigastric pain to exclude myocardial infarction (MI) as a differential diagnosis [3].
- Why it mimics pancreatitis: Severe abdominal/back pain (AAA rupture into the retroperitoneum causes intense back pain, just like pancreatitis). Both conditions can cause Cullen's sign and Grey Turner's sign (both are causes of retroperitoneal haemorrhage) [12].
- False positive elevated amylase can occur in ruptured AAA [2].
- Key distinguishing features:
- rAAA presents with the classic triad: abdominal pain + hypotension + pulsatile abdominal mass (though all three are present in only ~50%)
- Age > 65, male, smoking history, known AAA
- Haemodynamic instability is typically more dramatic and earlier than in pancreatitis
- CT angiography is diagnostic (retroperitoneal haematoma, contrast extravasation)
- Why it mimics pancreatitis: DKA commonly presents with abdominal pain, nausea, and vomiting. Additionally, DKA can cause a false positive elevated serum amylase [2].
- Key distinguishing features:
- Known diabetic (or new presentation of T1DM), polyuria, polydipsia, fruity breath (ketone bodies)
- Blood glucose markedly elevated, ketonaemia/ketonuria, metabolic acidosis with high anion gap
- Amylase elevation in DKA is usually salivary (not pancreatic) in origin — serum lipase is a better discriminator (normal in DKA, elevated in pancreatitis)
- Abdominal pain in DKA resolves with correction of ketoacidosis; if pain persists after correction, consider true pancreatitis (which can be precipitated by hypertriglyceridaemia in DKA)
| Condition | Why It Mimics Pancreatitis | Key Differentiator |
|---|---|---|
| Pericarditis | Epigastric/chest pain, worse lying flat, better leaning forward (same postural relief as pancreatitis!) | Pericardial friction rub; diffuse ST elevation with PR depression on ECG; troponin may be mildly elevated; amylase normal |
| Lower lobe pneumonia / Pleuritis | Referred pain to the upper abdomen via the phrenic nerve (C3–5 innervation of diaphragm) | CXR shows consolidation; cough, dyspnoea, productive sputum; amylase normal |
| Acute appendicitis (early) | Early appendicitis causes periumbilical visceral pain (T10 dermatome) that can overlap with epigastric pain; Valentino's sign = PPU fluid tracking to RLQ mimicking appendicitis [6] | Pain migrates to RLQ as parietal peritoneum becomes involved; McBurney's point tenderness, Rovsing's sign; amylase normal |
| Gastric volvulus | Severe epigastric pain with retching | Borchardt's triad: severe epigastric pain, retching without vomiting, inability to pass NG tube; CXR/AXR show distended stomach |
| Boerhaave's syndrome | Oesophageal rupture after forceful vomiting → severe epigastric/chest pain, mediastinitis | History of vomiting preceding the pain; subcutaneous emphysema; CXR shows pneumomediastinum; elevated salivary amylase in pleural fluid |
The differential is narrowed efficiently by a few targeted investigations:
| Investigation | What It Rules In/Out |
|---|---|
| Serum amylase/lipase ≥ 3× ULN | Confirms pancreatitis (but remember false positives: PPU, rAAA, DKA, macroamylasaemia) [2] |
| Serum lipase | More specific than amylase — helps exclude non-pancreatic causes of hyperamylasaemia |
| CXR (erect) | Pneumoperitoneum → PPU; consolidation → pneumonia; mediastinal air → Boerhaave's [2] |
| ECG + Troponin | Excludes MI [3] |
| LFT pattern | Cholestatic (↑ALP, ↑GGT, ↑bilirubin) → biliary cause; hepatocellular (↑↑ALT/AST) → hepatitis |
| Blood glucose + ketones + ABG | DKA |
| USG abdomen | Gallstones → biliary pancreatitis vs cholecystitis; dilated CBD → choledocholithiasis/cholangitis |
| CT abdomen with contrast | Gold standard when diagnosis is uncertain — differentiates pancreatitis, PPU, gangrenous cholecystitis, mesenteric ischaemia, rAAA [2] |
From the senior notes, the life-threatening DDx of acute abdomen [6] that overlap with pancreatitis presentation:
- Perforated viscus (PPU)
- Ruptured AAA
- Acute mesenteric ischaemia
- Severe pancreatitis (itself)
- Acute MI
- DKA
These require immediate recognition and management. Every patient with acute epigastric pain should have, at minimum: ECG, CXR, amylase/lipase, LFT, troponin, blood glucose, and ABG.
| Diagnosis | Pain Character | Key Sign | Key Investigation | Amylase |
|---|---|---|---|---|
| Acute pancreatitis | Constant, boring, radiates to back, relieved leaning forward | Cullen's/Grey Turner's (late) | Lipase ≥ 3× ULN; CT with contrast | ↑↑↑ (≥ 3× ULN) |
| PPU | Sudden "thunderclap", generalised | Board-like rigidity, absent bowel sounds | CXR: pneumoperitoneum | ↑ (false positive) |
| Acute cholecystitis | RUQ, constant | Murphy's sign positive | USG: wall thickening, pericholecystic fluid | Normal / mild ↑ |
| Cholangitis | RUQ/epigastric | Charcot's triad | USG: dilated CBD; cholestatic LFTs | Normal / mild ↑ |
| Mesenteric ischaemia | Severe, diffuse, out of proportion to exam | Surprisingly soft abdomen | CT angiography; lactate ↑ | ↑ (false positive) |
| Inferior MI | Crushing, pressure | Diaphoresis, dyspnoea | ECG: ST changes; Troponin ↑ | Normal |
| Ruptured AAA | Back/abdominal, sudden | Pulsatile mass, hypotension | CT angiography | ↑ (false positive) |
| DKA | Diffuse, crampy | Kussmaul breathing, fruity breath | Glucose ↑↑, ketones ↑, AG metabolic acidosis | ↑ (false positive) |
| Intestinal obstruction | Colicky, waves | Distension, tinkling bowel sounds | AXR: dilated loops, air-fluid levels | Normal / mild ↑ |
High Yield Summary
DDx of acute pancreatitis = DDx of acute epigastric pain. The major differentials from the notes and slides are:
- Peptic ulcer disease / PPU — CXR for pneumoperitoneum; PPU causes false-positive amylase
- Choledocholithiasis / Cholangitis / Cholecystitis — cholestatic LFTs, Murphy's sign, USG
- Hepatitis — massively elevated transaminases, viral serology
- Mesenteric ischaemia — pain out of proportion, AF patient, CT angiography
- Intestinal obstruction — colicky pain, absolute constipation, dilated loops on AXR
- Myocardial infarction — ECG + troponin must be checked in ALL patients with epigastric pain
- Ruptured AAA — pulsatile mass, hypotension, retroperitoneal haemorrhage (same Cullen's/Grey Turner's)
- DKA — glucose, ketones, ABG
Key principle: Serum lipase is more specific than amylase for pancreatitis. Always check CXR (to exclude PPU), ECG + troponin (to exclude MI), and consider CT with contrast when the diagnosis is uncertain.
Active Recall - Differential Diagnosis of Acute Pancreatitis
References
[2] Senior notes: maxim.md (Acute pancreatitis section) [3] Senior notes: felixlai.md (Acute pancreatitis section) [6] Senior notes: maxim.md (Acute abdomen section; Post-ERCP pancreatitis section) [11] Lecture slides: Acute pancreatitis.pdf (p8 — Diagnosis of acute pancreatitis) [12] Senior notes: felixlai.md (Cholangitis, Cholecystitis, and Ruptured AAA sections)
The Revised Atlanta Diagnostic Criteria (2012)
This is the universally accepted standard. The diagnosis of acute pancreatitis requires fulfilment of at least 2 out of 3 criteria [2][3]:
| Criterion | Domain | Description |
|---|---|---|
| 1. Clinical | History & Examination | Acute onset of persistent, severe, epigastric pain often radiating to the back [3] |
| 2. Biochemical | Laboratory | Elevation of serum amylase or lipase to ≥ 3× upper limit of normal (ULN) [3] |
| 3. Radiological | Imaging | Characteristic findings of acute pancreatitis on imaging — transabdominal USG, contrast-enhanced CT, or MRI [3] |
Why 2 out of 3? Because:
- If the clinical picture AND biochemistry are both classic (criteria 1 + 2), you do not need imaging to confirm the diagnosis — imaging is then reserved for assessing severity, identifying the aetiology, or detecting complications.
- If one criterion is equivocal (e.g., amylase only mildly raised, or the pain is atypical), imaging becomes essential to confirm the diagnosis.
- In practice, most patients are diagnosed clinically + biochemically, and imaging is added to assess severity rather than to make the diagnosis.
When Do You NEED Imaging to Diagnose?
If both clinical and biochemical criteria are clearly met (classic pain + amylase/lipase ≥ 3× ULN), imaging is not strictly required for diagnosis. You order CT to (1) assess severity and complications, (2) when the diagnosis is uncertain, or (3) when the patient is not improving as expected. Do NOT delay treatment to wait for imaging.
The following algorithm walks through the clinical decision-making from presentation to severity assessment:
Investigation Modalities — Detailed Breakdown
I'll walk through each investigation systematically: why we order it, what we're looking for, and how to interpret the results.
A. Baseline Bloods — "The Pancreatitis Panel"
Every patient with suspected acute pancreatitis should have the following ordered immediately [2][3]:
CBC, LRFT, CRP, glucose, Ca, cardiac markers ± ECG, pancreatic enzymes [2]
A1. Pancreatic Enzymes (The Diagnostic Markers)
These are the cornerstone of biochemical diagnosis. The word "amylase" comes from Greek amylon = starch; it breaks down starch. "Lipase" from Greek lipos = fat; it breaks down triglycerides.
| Parameter | Detail |
|---|---|
| Diagnostic cut-off | ≥ 3× ULN (normal: 30–100 U/L) [2][3] |
| Time course | Rises within 6–12 hours of onset, peaks at 24 hours, returns to normal within 3–5 days [2][3] |
| Correlation with severity | NO correlation between amylase level and severity [3] — a patient with amylase of 5000 can have mild disease, while one with 500 can be dying of necrotising pancreatitis |
| Persistent elevation | Should raise clinical suspicion of complications such as pseudocyst formation [3] |
Why does amylase rise? When acinar cells are damaged, they release their enzyme contents into the interstitial space → enzymes enter the bloodstream via lymphatics and venous drainage → measurable in serum.
Limitations — false negatives (amylase may NOT reach 3× ULN) [3]:
- Alcoholic pancreatitis — chronic alcohol damage to the parenchyma reduces its capacity to produce amylase ("burnt-out" acinar cells)
- Hypertriglyceridaemia-associated pancreatitis — triglycerides interfere with the amylase detection assay (laboratory artefact)
- Delayed presentation — if the patient presents > 3–5 days after onset, serum amylase may have already normalised
False positives (elevated amylase without pancreatitis) [2][3]:
- Perforated peptic ulcer (PPU)
- Ruptured AAA
- DKA
- Macroamylasaemia (amylase bound to immunoglobulin → high MW complex → not renally cleared → accumulates in serum)
- Intestinal obstruction, bowel ischaemia
- Acute cholecystitis
- Salivary gland disease (parotitis — remember, salivary glands also produce amylase)
Urine amylase [3]:
- Useful when serum amylase is equivocal or in delayed presentation
- Rises within 24–48 hours and persists for up to 1 week even after serum amylase has normalised [3]
- Because amylase is renally excreted and has a longer "tail" in the urine
| Parameter | Detail |
|---|---|
| Diagnostic cut-off | ≥ 3× ULN (normal: 10–140 U/L) [2] |
| Time course | Rises within 4–8 hours of onset, peaks at 24 hours, persists up to 2 weeks, returns to normal within 8–14 days [3] |
| Advantages over amylase | (1) More sensitive in alcoholic pancreatitis (2) Rises earlier and lasts longer → useful in delayed presentation > 24 hours (3) More specific for pancreatic disease [2][3] |
Why is lipase more specific? Amylase is produced by many tissues (salivary glands, lungs, fallopian tubes, small intestine), so many non-pancreatic conditions raise amylase. Lipase is produced almost exclusively by the pancreas, so its elevation is more reliably pancreatic in origin.
False positives for lipase [3]:
- Post-ERCP
- Pancreatic tumours
- Acute cholecystitis (mild elevation, usually < 3× ULN)
Amylase vs Lipase — What to Remember
Lipase is the superior marker. It is more sensitive (especially in alcoholic pancreatitis), more specific (fewer false positives), rises earlier, and lasts longer. If you can only order one test, order lipase. However, in practice, both are usually ordered together. Pancreatic enzymes are NOT indicative of severity [2] — a common exam pitfall.
| Feature | Serum Amylase | Serum Lipase |
|---|---|---|
| Onset of rise | 6–12 hours | 4–8 hours |
| Peak | 24 hours | 24 hours |
| Duration | 3–5 days | 8–14 days |
| Better for delayed presentation? | No (may have normalised) | Yes |
| Better for alcoholic pancreatitis? | No (low production) | Yes |
| Specificity | Lower (many sources) | Higher |
| Severity correlation | None | None |
| Finding | Interpretation / Pathophysiology |
|---|---|
| Leukocytosis [11] | Inflammatory response — cytokines (IL-6, TNF-α) stimulate bone marrow to release neutrophils. Part of SIRS criteria. |
| ↑ Haematocrit | Haemoconcentration due to extravasation of intravascular fluid into 3rd spaces (sequestration of oedematous fluid in retroperitoneum) [3]. A rising Hct suggests inadequate resuscitation; a fall by ≥ 10% at 48h is a Ranson's criterion indicating significant fluid loss. |
| ↓ Haemoglobin (later) | If retroperitoneal haemorrhage occurs (necrotising pancreatitis, pseudoaneurysm rupture) |
The LFT pattern is crucial for establishing aetiology — specifically, is this biliary pancreatitis?
| Finding | Interpretation |
|---|---|
| ↑ Conjugated bilirubin | Obstruction of CBD by gallstone at ampulla, or compression by oedematous head of pancreas |
| ↑ AST, ALT | Hepatocellular injury from biliary obstruction. ALT > 150 U/L has a positive predictive value of > 85% for gallstone pancreatitis (a very useful clinical rule) |
| ↑ ALP | Cholestatic pattern — suggests biliary cause. Suspect gallstone pancreatitis if ↑ALP [2] |
| Normal LFTs do not rule out biliary aetiology [3] | The stone may have passed by the time bloods are drawn; LFTs can normalise rapidly |
| Finding | Interpretation |
|---|---|
| ↑ Creatinine and BUN | Severe fluid loss may lead to prerenal azotaemia — third-spacing of up to > 6 L into the retroperitoneum reduces effective circulating volume → reduced renal perfusion → rising creatinine and BUN [3]. BUN rising despite IV fluids is a Ranson's 48h criterion and indicates inadequate resuscitation or intrinsic renal injury. |
| Marker | Role |
|---|---|
| ↑ CRP | Not useful for diagnosis, but critical for severity assessment. CRP > 150 mg/L at 48 hours predicts severe attack [2][13]. CRP is an acute-phase protein synthesised by the liver in response to IL-6 — it takes 24–48 hours to peak, which is why the 48-hour value is prognostic. |
| IL-6, IL-8, TNF-α | Biochemical markers for severity assessment [13] — research tools. IL-6 rises earlier than CRP (peaks at 24–36 hours) and drives CRP synthesis. Trypsinogen activation peptide (TAP) [13] is released when trypsinogen is activated to trypsin — a direct marker of disease activity, mainly in research settings. |
| Finding | Interpretation |
|---|---|
| Hyperglycaemia | Islet cell damage → insulin deficiency; stress response → counter-regulatory hormones (cortisol, glucagon, catecholamines) → elevated glucose. Glucose > 11.1 mmol/L at admission is a Ranson's criterion. |
| Hypoglycaemia (rare) | Excessive insulin release from damaged islets (uncommon) |
| Finding | Interpretation |
|---|---|
| Hypocalcaemia | Complexing with fatty acids (saponification/fat necrosis) produced by activated lipases, as well as hypoalbuminaemia [3]. Ca²⁺ < 2 mmol/L at 48 hours is a Ranson's criterion. Severe hypocalcaemia → tetany, prolonged QT interval. |
Always check corrected calcium (for albumin) or ionised calcium to assess true calcium status.
| Finding | Interpretation |
|---|---|
| TG > 11.3 mmol/L (> 1000 mg/dL) | Hypertriglyceridaemia as the aetiological cause. Note: very high TG can also interfere with amylase assay → false-negative amylase [3]. |
Troponin (TnI, TnT) to exclude myocardial infarction (MI) as a differential diagnosis of epigastric pain [3]
This is mandatory in every patient with acute epigastric pain. An inferior MI can perfectly mimic pancreatitis. ECG may show ST changes in MI, or non-specific ST-T changes from the metabolic stress of severe pancreatitis itself.
| Finding | Interpretation |
|---|---|
| Metabolic acidosis | Lactic acidosis from hypovolaemia/hypoperfusion; base deficit > 4 mEq/L is a Ranson's 48h criterion |
| Hypoxaemia (PaO₂ < 8 kPa / 60 mmHg) | Ranson's 48h criterion; indicates ARDS, pleural effusion, or diaphragmatic splinting |
| Respiratory alkalosis (early) | Pain-driven tachypnoea → hyperventilation → CO₂ washout |
B. Radiological Investigations
Purpose: Rule out perforation (PPU) — look for pneumoperitoneum (free air under diaphragm) — and identify other DDx [2].
| Finding | Interpretation |
|---|---|
| Pneumoperitoneum | Perforated viscus (NOT pancreatitis) — this is the key reason to order a CXR |
| Left-sided pleural effusion | Transdiaphragmatic lymphatic drainage of enzyme-rich exudative fluid from the inflamed pancreas; also seen in ARDS |
| Basal atelectasis | Diaphragmatic splinting from adjacent inflammation |
| Pulmonary infiltrates | ARDS in severe cases |
AXR is a quick, cheap, widely available initial imaging. It does not diagnose pancreatitis directly, but shows supportive indirect signs and excludes other pathology.
| Finding | Description | Pathophysiological Basis |
|---|---|---|
| Sentinel loop sign [2][3] | Localised dilated loop of small intestine (usually jejunum) in the LUQ/epigastrium | Localised ileus of a segment of small intestine adjacent to the inflamed pancreas — reflex inhibition of peristalsis via splanchnic nerves [3] |
| Colonic cut-off sign [2][3] | Paucity of air in the colon distal to the splenic flexure | Functional spasm of the descending colon secondary to pancreatic inflammation [3] — the inflamed pancreatic tail/body irritates the adjacent transverse/descending colon |
| Obliteration of psoas outline [2] | Loss of the normally visible psoas muscle shadow | Retroperitoneal fluid accumulation [2] — fluid from pancreatic inflammation dissects into the retroperitoneal space, obscuring the psoas shadow |
| Ground-glass appearance [3] | Hazy opacity in the abdomen | Indicates presence of acute peripancreatic fluid collection [3] — free fluid in the peritoneal/retroperitoneal space |
| Absent pneumoperitoneum | No free air under diaphragm | Helps exclude PPU |
| Pancreatic calcifications | Calcification at the level of L1–L2 | Suggests pre-existing chronic pancreatitis (not acute pancreatitis per se) |
USG is the first-line imaging in acute pancreatitis — not primarily to diagnose pancreatitis (which is usually biochemically confirmed), but to identify the aetiology (especially gallstones).
| Finding | Interpretation |
|---|---|
| Gallstones in gallbladder/CBD | Biliary pancreatitis — this is the main reason to order USG |
| Swollen pancreas (diffusely enlarged, hypoechoic) [2] | Oedematous pancreatitis — however, pancreas is seen in only ~50% of cases [2] due to overlying bowel gas |
| Peripancreatic fluid collection (anechoic collection) [2][3] | Complication — acute peripancreatic fluid collection |
| Dilated CBD (> 6 mm, or > 10 mm post-cholecystectomy) | CBD obstruction — stone, tumour, or oedema of pancreatic head |
| Associated cholecystitis | Thickened gallbladder wall, pericholecystic fluid |
Limitations [3]:
- Distal (lower end) of CBD may be obscured by bowel gas — the intrapancreatic portion of the CBD sits behind the duodenum and is frequently not visualised
- Cannot clearly delineate extra-pancreatic spread of pancreatic inflammation or identify necrosis within the pancreas — USG lacks the resolution and penetration for this; CT is needed
USG in Pancreatitis — Know Its Role
USG does NOT reliably diagnose pancreatitis (it misses the pancreas ~50% of the time due to bowel gas). Its primary role is to identify gallstones as the aetiology. Every patient with acute pancreatitis should have a USG abdomen to look for gallstones, even if the diagnosis is already confirmed biochemically.
B4. CT Abdomen with Contrast — The Gold Standard [3][2][13]
This is the most important imaging modality for acute pancreatitis. Let's break it down comprehensively.
Why CT? CT provides:
- Diagnostic confirmation when clinical + biochemical criteria are equivocal
- Severity assessment (necrosis, fluid collections)
- Complication detection
- Aetiological clues (gallstones, tumours)
- Exclusion of other diagnoses
Gold standard for the disease with Sensitivity = 90% and Specificity = 100% [3]
| Finding | Description | What It Means |
|---|---|---|
| Focal or diffuse enlargement of pancreas [2][3] | Pancreas appears swollen, sometimes with loss of normal lobular architecture | Oedematous pancreatitis |
| Heterogeneous contrast enhancement [2][3] | Uneven enhancement pattern of the pancreatic parenchyma | Varying degrees of inflammation and oedema |
| Peripancreatic fat stranding [2] | Increased density/haziness of the fat surrounding the pancreas | Inflammation extending beyond the pancreas into peripancreatic tissues |
| Hypoenhancement on contrast CT [2] | Areas of the pancreas that do NOT take up IV contrast | Pancreatic necrosis — non-viable tissue has lost its blood supply and therefore cannot enhance. This is why contrast is essential [3] |
| Gas within areas of necrosis [2] | Air bubbles seen within necrotic pancreatic or peripancreatic tissue | Strongly suggestive of infected necrosis (gas produced by bacteria, usually Gram-negatives) |
| Peripancreatic fluid collections | Defined fluid collections adjacent to pancreas | APFC (< 4 weeks, no wall) vs pseudocyst (≥ 4 weeks, defined wall) |
Contrast is essential to detect the presence of pancreatic necrosis [3]
Without IV contrast, you cannot distinguish viable (enhancing) pancreatic tissue from necrotic (non-enhancing) tissue. An unenhanced CT might show a swollen pancreas, but you would miss necrosis entirely — and necrosis is what determines the difference between interstitial oedematous pancreatitis (good prognosis) and necrotising pancreatitis (potentially fatal).
- CT changes may NOT occur within the first 24 hours of presentation [3]
- Best done at 72–96 hours after admission to accurately assess the full extent of necrosis [2]
- Earlier CT (within 24–48h) is indicated if:
Don't CT Too Early!
A CT done within the first 24 hours often underestimates the severity of pancreatitis because necrosis has not yet fully demarcated. The optimal window is 72–96 hours. However, if the patient has organ failure or you're not sure of the diagnosis, don't delay — CT early. Clinical judgment trumps timing rules.
This is a prognostic scale based on CT findings that combines the grade of pancreatitis with the extent of necrosis [3]:
Score = Grade of pancreatitis (0–4) + Percentage of necrosis (0–6) [2]
Grade of Pancreatitis:
| Grade | CT Appearance | Points |
|---|---|---|
| A | Normal pancreas | 0 |
| B | Focal or diffuse enlargement | 1 |
| C | Pancreatic or peripancreatic inflammation | 2 |
| D | Single peripancreatic fluid collection | 3 |
| E | Multiple fluid collections or retroperitoneal air | 4 |
Percentage of Necrosis:
| Necrosis Extent | Points |
|---|---|
| 0% (no necrosis) | 0 |
| < 30% | 2 |
| 30–50% | 4 |
| > 50% | 6 |
Interpretation [3]:
- CTSI 0–3: Low morbidity and mortality
- CTSI 4–6: Moderate morbidity
- CTSI 7–10: Morbidity 92%, mortality 17% [3]
| Feature | Detail |
|---|---|
| Advantages over CT | Higher sensitivity for diagnosis of early acute pancreatitis; better characterisation of pancreatic and bile duct anatomy and complications [3]; no ionising radiation; no need for iodinated contrast (safer in renal impairment or contrast allergy) |
| MRCP | Magnetic resonance cholangiopancreatography is comparable to ERCP for the detection of choledocholithiasis [3] — it provides a non-invasive "map" of the biliary and pancreatic duct system |
| When to use | When CT is contraindicated (contrast allergy, renal impairment), for detailed duct anatomy, or to look for subtle choledocholithiasis missed on USG |
| Limitation | Less widely available, takes longer, motion artefact in unwell/agitated patients |
ERCP and MRCP are not routinely done because the culprit stone usually passes spontaneously [2]. However, they are indicated in specific situations:
| Indication | Modality |
|---|---|
| Suspected biliary pancreatitis (stone found on USG, septic/cholangitis) | ERCP within 24–72 hours for therapeutic sphincterotomy and stone extraction [2] |
| Moderate suspicion of CBD stone but not confirmed | MRCP or EUS first to confirm before proceeding to ERCP (to avoid unnecessary ERCP risk) |
| Uncertain diagnosis / severe case (last resort) | ERCP [2] |
ERCP — Diagnostic vs Therapeutic
ERCP is primarily a therapeutic procedure in the context of biliary pancreatitis (sphincterotomy + stone extraction). For diagnosis of CBD stones, prefer non-invasive MRCP or EUS first — ERCP carries a 4% risk of post-ERCP pancreatitis, which is the last thing you want in someone who already has pancreatitis.
From the lecture slides [13]:
Assessment of disease severity involves:
- Clinical scoring systems: Ranson and Glasgow systems (require 48 hours for full assessment), APACHE II and APACHE-O
- Biochemical markers: C-reactive protein, Interleukin-8 or 6, Tumor necrosis factor, Trypsinogen activation peptide (TAP)
- Radiological studies: Dynamic contrast CT scan — pancreatic inflammation and peripancreatic fluid collection (Balthazar system), MRI [13]
Modified Marshall Scoring System (for defining organ failure)
This is the scoring system used in the Revised Atlanta Classification to define organ failure:
| Organ System | Score 0 | Score 1 | Score 2 (= Organ Failure) | Score 3 | Score 4 |
|---|---|---|---|---|---|
| Respiratory (PaO₂/FiO₂) | > 400 | 301–400 | 201–300 | 101–200 | ≤ 100 |
| Renal (Creatinine μmol/L) | < 134 | 134–169 | 170–310 | 311–439 | > 439 |
| Cardiovascular (SBP mmHg) | > 90 | < 90, responds to fluids | < 90, not responding to fluids | < 90, pH < 7.3 | < 90, pH < 7.2 |
- A score of ≥ 2 in any organ system = organ failure
- Transient organ failure (resolving within 48 hours) = moderately severe
- Persistent organ failure ( > 48 hours) = severe acute pancreatitis [13]
Definition of severe pancreatitis: pancreatitis associated with organ failure and/or local complications e.g. necrosis, abscess formation, or pseudocyst [14]
| Purpose | Investigation | Key Finding |
|---|---|---|
| Confirm diagnosis | Serum amylase/lipase | ≥ 3× ULN |
| Exclude DDx | CXR (pneumoperitoneum → PPU), ECG + troponin (MI), blood glucose + ketones (DKA) | |
| Identify aetiology | USG (gallstones), LFTs (cholestatic pattern → biliary), TG level, Ca²⁺, drug history | |
| Assess severity | Ranson's (0h + 48h), APACHE II (admission + daily), CRP at 48h, CT at 72–96h | Ranson ≥ 3, APACHE II ≥ 8, CRP > 150, CTSI 7–10 |
| Detect necrosis | CT abdomen with contrast at 72–96h | Hypoenhancement, gas |
| Detect CBD stones | USG → MRCP / EUS → ERCP (therapeutic) | Dilated CBD, visible stone |
| Detect complications | CT with contrast; angiography if pseudoaneurysm suspected | Fluid collections, vascular complications |
High Yield Summary
Diagnostic Criteria (Revised Atlanta): 2 out of 3 — (1) Typical epigastric pain radiating to back, (2) Amylase or lipase ≥ 3× ULN, (3) Characteristic imaging findings.
Pancreatic Enzymes: Lipase is superior to amylase — more sensitive (especially alcoholic), more specific, rises earlier, lasts longer. Neither correlates with severity.
False positive amylase: PPU, ruptured AAA, DKA, macroamylasaemia, bowel ischaemia.
USG abdomen: First-line imaging — primarily to identify gallstones as the aetiology. Pancreas only seen ~50% of the time.
CT abdomen with contrast: Gold standard (Sn 90%, Sp 100%). Contrast essential to detect necrosis (hypoenhancement). Best at 72–96 hours. Gas in necrosis = infected necrosis.
AXR signs: Sentinel loop sign (localised ileus), colonic cut-off sign (descending colon spasm), obliteration of psoas outline (retroperitoneal fluid).
Severity assessment: Ranson's (GALAW + CHOBBS, ≥ 3 = severe, needs 48h), APACHE II (≥ 8, can calculate daily), CRP > 150 at 48h, Balthazar CTSI (grade 0–4 + necrosis 0–6), Modified Marshall Score for organ failure.
Always check: ECG + troponin (exclude MI), CXR (exclude PPU).
Active Recall - Diagnosis of Acute Pancreatitis
[2] Senior notes: maxim.md (Acute pancreatitis section) [3] Senior notes: felixlai.md (Acute pancreatitis section) [11] Lecture slides: Acute pancreatitis.pdf (p8 — Diagnosis of acute pancreatitis) [13] Lecture slides: Acute pancreatitis.pdf (p10 — Assessment of disease severity) [14] Lecture slides: Acute pancreatitis.pdf (p11 — Definition of severe pancreatitis)
Management of Acute Pancreatitis
Before diving into specifics, the lecture slides frame two guiding principles beautifully [15]:
Aim in treatment of acute pancreatitis:
- To identify patients with severe pancreatitis to institute directed therapy in the early phase of disease
- To prevent progression of disease from acute oedematous state to necrotising / haemorrhagic state [15]
Everything we do in management serves one of these two goals. The first is about risk stratification (scoring systems, CRP, CT). The second is about maintaining pancreatic perfusion (aggressive fluids) and removing the inciting cause (ERCP for gallstones). If you remember nothing else, remember: fluids prevent necrosis, and necrosis kills.
The management summary from the lecture slides [16]:
Summary:
- Conservative management of uncomplicated acute pancreatitis
- Early ERCP and antibiotics to treat acute biliary pancreatitis and cholangitis
- IV carbapenem for necrotising pancreatitis
- Percutaneous / endoscopic / surgical drainage of infected pancreatic necrosis
- Endoscopic or (rarely) open cystogastrostomy for persistent large pseudocysts [16]
1. General Supportive Management (All Patients)
This is the backbone of management — most patients with acute pancreatitis (80% with mild disease) recover with supportive care alone [16].
This is the single most important intervention in acute pancreatitis. Here's why, explained from first principles:
The problem: Pancreatic inflammation → massive third-spacing of fluid into the retroperitoneum, peritoneal cavity, and interstitial spaces (up to > 6 litres in severe cases). This causes intravascular volume depletion → hypoperfusion of the pancreas → ischaemic necrosis (the very thing that converts mild disease into lethal necrotising disease) [15].
The solution: Aggressive early fluid resuscitation to maintain intravascular volume and pancreatic perfusion.
| Parameter | Detail |
|---|---|
| Access | Establish 2 large-bore (16-Gauge) peripheral IV cannulae [3] |
| Fluid choice | Lactated Ringer's (LR) solution may be superior to normal saline (NS) in reducing SIRS [3] — LR is more physiological (contains lactate as a buffer, has lower chloride content, reducing risk of hyperchloraemic metabolic acidosis). Multiple RCTs now support LR as the fluid of choice. |
| Rate | Goal-directed: typically 5–10 mL/kg/hr initially in the first 12–24 hours, then titrated |
| Target | Urine output ≥ 0.5 mL/kg/hr — this is the minimum indicating adequate renal perfusion [3]. 1.0 mL/kg/hr indicates optimal renal perfusion and function with good hydration [3]. |
| Monitoring | Foley catheter with Q1H monitoring [3] to track UO precisely |
Why Lactated Ringer's Over Normal Saline?
NS has a supraphysiological chloride concentration (154 mEq/L vs plasma ~100 mEq/L). Large-volume NS resuscitation causes hyperchloraemic metabolic acidosis, which can worsen the metabolic derangement already present in pancreatitis. LR is buffered and more closely matches plasma composition. The anti-inflammatory effect of LR (via lactate metabolism to bicarbonate) also helps reduce SIRS.
- Pulse oximetry and ABG monitoring are necessary to assess oxygenation and acid-base status [3]
- Supplemental O₂ to maintain SpO₂ > 95%
- Why? Severe pancreatitis causes hypoxaemia through multiple mechanisms: pleural effusions, ARDS, diaphragmatic splinting, atelectasis
- Correct electrolyte and glucose disturbances [2]
- Hypocalcaemia: Replete with IV calcium gluconate (monitor ECG — prolonged QTc is dangerous)
- Hypokalaemia/Hypomagnasaemia: Common from vomiting and third-spacing
- Hyperglycaemia: Sliding-scale insulin; avoid over-correction (risk of hypoglycaemia, especially if glucagon-producing α-cells are also damaged)
| Intervention | Indication | Rationale |
|---|---|---|
| NPO | Only if necessary — until nausea and vomiting settle [3] | The old dogma of prolonged "pancreatic rest" (keeping patients nil by mouth for days) is outdated. Current evidence strongly favours early oral feeding when tolerated. |
| NG suction | If ileus or protracted vomiting [3][2] | Decompresses the stomach, reduces aspiration risk, and decreases neurohormonal stimulation of pancreatic secretion [3] (gastric distension triggers CCK and secretin release → stimulates pancreatic enzyme secretion → worsens the disease) |
This is a paradigm shift in pancreatitis management. The old approach was "rest the pancreas" — starve the patient. This is wrong and harmful.
It is NO longer acceptable to "rest the pancreas" by avoiding enteral nutrition [3]
Why enteral feeding is critical:
- Early enteral feeding is associated with lower rates of infection, surgical intervention, and length of stay [3]
- Delay in enteral feeding may contribute to the development of intestinal ileus and feeding intolerance [3]
- Enteral nutrition maintains gut mucosal barrier integrity → prevents bacterial translocation → reduces risk of infected necrosis (recall the pathophysiology: gut barrier breakdown → bacterial translocation → infected necrosis → sepsis → death)
Route of enteral feeding:
| Route | Detail |
|---|---|
| Oral (first choice for mild AP) | Encourage early oral feeding if mild [2] — start with low-fat solid diet as tolerated |
| NG tube | Nasogastric feeding is safe and effective [3] — contrary to previous belief that NG feeding stimulates the pancreas. Multiple RCTs show NG is as good as NJ. |
| NJ tube | Nasojejunal feeding — bypasses the stomach and duodenum, theoretically providing less pancreatic stimulation. NJ tube can be attempted if there is evidence of feeding intolerance via NG [3]. |
| NG or NJ: similar efficacy and safety [2] | Start with NG; escalate to NJ if not tolerated |
Parenteral nutrition (TPN):
- Should only be considered if the enteral route is not available, not tolerated, or caloric requirements cannot be met [3]
- TPN has higher infection rates (line sepsis) and does not maintain gut mucosal barrier
- In the slides for severe pancreatitis: Nutritional support (TPN + early enteral feeding) [17] — meaning TPN is a supplement, not a replacement
Recommended nutrient requirements in severe AP [3]:
| Nutrient | Requirement |
|---|---|
| Energy | 25–35 kcal/kg/day |
| Protein | 1.2–1.5 g/kg/day |
| Carbohydrates | 3–6 g/kg/day |
| Lipids | 2 g/kg/day |
- Monitor vitals, I/O, RFT, Ca, glucose ± ABG [2]
- Frequency: Vitals Q1–4H depending on severity; bloods at least daily initially
- Serial CRP (48-hour value is prognostic)
- Ranson's parameters at 48 hours
2. Medical Treatment
Pain control is essential — pancreatitis is excruciatingly painful, and uncontrolled pain causes tachycardia, hypertension, and splanchnic vasoconstriction (worsening pancreatic perfusion).
| Agent | Role | Notes |
|---|---|---|
| Tramadol / Pethidine (meperidine) [2] | First-line opioid analgesics | Tramadol is a weak μ-opioid agonist + serotonin/noradrenaline reuptake inhibitor. Pethidine has traditionally been preferred because it is said to cause less sphincter of Oddi spasm than morphine. |
| Paracetamol | Adjunctive, mild pain | Safe baseline analgesia, opioid-sparing effect |
| NSAIDs | Avoid [2] | NSAIDs worsen pancreatitis [2] — they impair renal blood flow (prostaglandin-dependent) in an already hypovolaemic patient, and may exacerbate mucosal injury. Exception: PR indomethacin is used for prevention of post-ERCP pancreatitis, but this is a specific prophylactic setting, not treatment of established pancreatitis. |
| Morphine | AVOID — potential to cause sphincter of Oddi spasm [3][2] | Morphine contracts the sphincter of Oddi → theoretically worsens pancreatic duct obstruction → worsens pancreatitis. Although the clinical significance is debated, it remains a standard teaching point and exam favourite. Avoid morphine; ↑ sphincter of Oddi pressure [2]. |
The Morphine Question
In exams, the answer is: avoid morphine in acute pancreatitis because it causes sphincter of Oddi spasm. In real clinical practice, the evidence for this is weak, and some guidelines now consider morphine acceptable if other agents fail. But for HKUMed exams, stick with the teaching: morphine should be AVOIDED [3].
- PPI for prophylaxis of acute stress ulcer [2]
- Why? Critically ill patients are at high risk of stress-related mucosal disease (Curling's ulcer in burns, Cushing's ulcer in raised ICP). In pancreatitis, haemodynamic instability and SIRS increase gastric acid-related mucosal injury risk. Omeprazole or pantoprazole IV covers this.
This is one of the most commonly tested and nuanced topics in pancreatitis management.
The key principle: Prophylactic antibiotics are generally NOT recommended [3][2][16]
Why not? Most pancreatitis is a sterile inflammatory process. Routine antibiotics:
- Do not reduce mortality or infected necrosis in uncomplicated pancreatitis (multiple RCTs and meta-analyses)
- Promote antibiotic resistance and Clostridioides difficile infection
- May give a false sense of security
When ARE antibiotics indicated? [3][2]
| Indication | Antibiotic Choice | Rationale |
|---|---|---|
| Concurrent cholangitis (LFT shows cholestatic pattern) [2] | IV Augmentin (amoxicillin-clavulanate) [2] | Biliary sepsis from CBD stone causing both cholangitis and pancreatitis — treat the infection |
| Infected pancreatic necrosis [16] | IV carbapenem (imipenem or meropenem) [3][16] | IV carbapenem for necrotising pancreatitis [16]. Carbapenems are chosen because they penetrate necrotic pancreatic tissue well (good lipophilicity and tissue penetration). Target enteric Gram-negative organisms (E. coli, Klebsiella) that translocate from the gut. |
| Necrosis > 30% on CT (may be considered) [3] | Carbapenems, fluoroquinolones + metronidazole [3] | Antibiotics that are known to penetrate pancreatic necrosis should be used, including carbapenems, fluoroquinolones, and metronidazole [3] |
| SIRS with evidence suggesting infection [3] | Case-by-case | Increased CRP with other evidence supporting possibility of infection [3] |
Why carbapenems specifically?
- "Carba-" = carbapenem nucleus; "penem" = β-lactam subclass. These are the broadest-spectrum β-lactams, covering Gram-positives, Gram-negatives (including ESBL-producers), and anaerobes.
- Crucially, they achieve therapeutic concentrations in necrotic pancreatic tissue — most other antibiotics cannot penetrate avascular necrotic debris effectively.
Antibiotics in Pancreatitis — The Exam Rule
No prophylactic antibiotics for uncomplicated pancreatitis. Give antibiotics ONLY for: (1) cholangitis, (2) infected necrosis, (3) SIRS with strong suspicion of infection. The drug of choice for infected necrosis is imipenem or meropenem (carbapenems).
3. Management of Biliary Pancreatitis
Biliary pancreatitis has specific additional management steps because the cause is treatable — remove the gallstones, and you prevent recurrence.
Emergency ERCP for biliary pancreatitis [17]
Treatment protocol of acute biliary pancreatitis: Emergency ERCP ± EPT (endoscopic papillotomy/sphincterotomy) → Elective cholecystectomy [18]
| Aspect | Detail |
|---|---|
| Indications [3][2] | Patients with jaundice, acute cholangitis, or evidence of persistent CBD stones leading to biliary pancreatitis — arrange within 24–72 hours after admission for endoscopic sphincterotomy and stone extraction [3][2] |
| Patients with no identifiable cause — to rule out CBD stones, strictures, or neoplasms [3] | |
| Suspected pancreatic ductal disruption (e.g. traumatic pancreatitis) [3] | |
| What is done | Endoscopic sphincterotomy (EPT = endoscopic papillotomy — cutting the sphincter of Oddi) + stone extraction with balloon or basket |
| Contraindications [3] | Gastric or bowel obstruction, altered anatomy in post-surgical state (e.g. gastrectomy with Billroth II or Roux-en-Y) [3] |
| Important caveat | ERCP is NOT indicated in the absence of CBD obstruction [3] — if there's no evidence of biliary obstruction (normal LFTs, no dilated CBD, no visible stone), ERCP is unnecessary and carries risk (post-ERCP pancreatitis ~4%) |
Decision tree for suspected CBD stones [3]:
- Clinical suspicion of CBD stone is high → ERCP
- Clinical suspicion is moderate → MRCP or EUS to exclude CBD stones before proceeding to cholecystectomy
- Clinical suspicion is low → Cholecystectomy with intraoperative cholangiogram (IOC) during the procedure
- Decompress and drain the biliary system in biliary pancreatitis [3]
- Indicated in patients who are unable to perform ERCP [3] — e.g. post-Billroth II gastrectomy (the duodenum is not accessible endoscopically), failed ERCP, unstable patient
- Alternative: PTBD to decompress biliary tract if unfit for ERCP [2]
- Open surgical drainage — rarely performed nowadays [3]
- Last resort when ERCP and PTBD are both impossible
After resolving the acute episode, the gallbladder must be removed to prevent recurrence (recurrence rate without cholecystectomy is ~30–40% within 6 weeks).
Elective cholecystectomy — laparoscopic or open [18]
| Scenario | Timing |
|---|---|
| Mild pancreatitis | Cholecystectomy can be performed safely within a week of recovery and in the same index hospitalisation [3][2] — Lap cholecystectomy within the same hospitalisation [2]. Delaying discharge without cholecystectomy risks recurrent pancreatitis before the outpatient surgery date. |
| Severe necrotising pancreatitis | Cholecystectomy should be delayed until active inflammation subsides and fluid collections resolve or stabilise (interval cholecystectomy) [3] — typically 6 weeks or more |
Intraoperative cholangiography (IOC) is performed during cholecystectomy to rule out persistent choledocholithiasis [3].
4. Management of Severe Pancreatitis
Principles of management of severe pancreatitis [17]:
- Close monitoring (haemodynamic, urine output)
- Fluid resuscitation
- Cardiovascular support
- Renal support
- Mechanical ventilation
- Prophylactic potent antibiotic
- Emergency ERCP for biliary pancreatitis
- Nutritional support (TPN + early enteral feeding) [17]
Consult ICU for organ support [2]:
| Organ System | Support |
|---|---|
| GI | Enteral feeding (NJ) → TPN if intolerant [2] |
| CVS | CVP monitoring, inotropes (noradrenaline/vasopressin for vasodilatory shock from SIRS) [2] |
| Respiratory | Intubation and mechanical ventilation for ARDS or respiratory failure [2] |
| Renal | Haemodialysis (HD) for AKI unresponsive to fluid resuscitation [2] |
| Abdominal | Measure intra-abdominal pressure (IAP) for abdominal compartment syndrome [2] — IAP > 20 mmHg with new organ failure defines abdominal compartment syndrome, which may require decompressive laparotomy |
Surgery indicated if:
- Infected pancreatic necrosis
- Progressive clinical deterioration despite maximal conservative and ICU management [2]
This is one of the most important modern concepts in pancreatitis surgery. The key principle is minimise surgical aggression — infected necrosis is managed with a graduated ("step-up") approach rather than rushing to open necrosectomy.
The Step-Up Approach [3][2][19]
Definitive treatment for infected pancreatic necrosis [19]:
- Radiologically-guided drainage → Dilatation of tract and video-assisted retroperitoneal debridement (VARD)
- Endoscopic ultrasound drainage → Stent insertion ± endoscopic debridement
- Necrosectomy (surgical debridement) — Open (standard) or minimally invasive approaches (for selected cases) [19]
Step 1: Antibiotics [3]
- Empirical antibiotics that penetrate pancreatic necrosis [3]
- Carbapenem monotherapy (imipenem/meropenem) OR Ceftazidime/Cefepime/Fluoroquinolone + Metronidazole [3]
Step 2: Drainage [3]
- Percutaneous catheter drainage or endoscopic drainage is used as the first step to stabilise the patient's overall clinical status [3]
- Drainage "buys time" and allows the lesion to become more walled off and safer to treat [3]
- Primary percutaneous catheter drainage may be the only intervention required in 1/3 to 1/2 of patients [3]
Step 3: Delayed necrosectomy [3]
- Resection of necrosis by minimally-invasive or endoscopic means is performed as a second procedure 3–4 weeks later if necessary [3]
- Should be delayed to at least 3–4 weeks after onset [3] — why?
- Allow sequestration and demarcation of the necrosis — necrotic tissue separates from viable tissue over time, making debridement easier and safer
- Reduce risk of bleeding, disseminated infection, and collateral damage to adjacent organs [3]
- Continued conservative treatment allows a minimally invasive debridement to be performed at a later date [3]
- Minimally invasive preferred: endoscopic or percutaneous > open [2]
- Open necrosectomy is reserved for patients who fail to improve with less invasive approaches [3]
Why Delay Surgery?
Early open necrosectomy (within the first 2 weeks) carries mortality rates of 40–75% because the necrotic tissue is not yet demarcated from viable tissue — the surgeon ends up removing viable pancreas and causing massive haemorrhage. Waiting ≥ 4 weeks allows the necrosis to "wall off" (WON), creating a defined plane that can be safely debrided with much lower morbidity.
6. Management of Pancreatic Fluid Collections
This follows the Revised Atlanta classification timeline (< 4 weeks vs ≥ 4 weeks) and whether necrosis is present:
- Resolve spontaneously within 7–10 days without the need for drainage [3]
- Management: observation and serial imaging
- No intervention needed unless they become infected (rare)
Treatment strategy for pancreatic pseudocyst [20]:
- Observe
- If cyst > 5 cm by 6 weeks → internal drainage
- If cyst develops complication (e.g. bleeding, rupture, infection, obstruction) → external drainage [20]
| Management | Detail |
|---|---|
| Watchful waiting | Allow wall to "mature" (thicken) — 50% resolve spontaneously [2]. Wait at least 6 weeks for the wall to mature enough to hold sutures/stents. |
| Internal drainage (preferred) | For symptomatic "mature" pseudocyst with size > 5–6 cm [20][2]: |
| Cystogastrostomy (endoscopic or operative) — creates a communication between the pseudocyst and the posterior gastric wall [20] | |
| Cystoduodenostomy (operative) — connects pseudocyst to duodenum [20] | |
| Cystojejunostomy (operative) — Roux-en-Y loop [20] | |
| EUS-guided cystogastrostomy is first-line [2] — avoids open surgery | |
| External drainage | If cyst develops complications: bleeding, rupture, infection, obstruction [20] |
| Percutaneous catheter drainage — higher recurrence rate, risk of pancreatocutaneous fistula [2] |
| Management | Detail |
|---|---|
| If sterile + asymptomatic | Conservative management with serial monitoring |
| If symptomatic or infected | EUS/ERCP-guided transmural drainage ± necrosectomy (first-line) [2] |
| Percutaneous drainage (higher recurrence, fistula risk) [2] | |
| Surgical debridement (open/lap) with external/internal drainage [2] |
This deserves special mention because of a critical safety rule:
- Angiography is the definitive diagnostic test and has been used increasingly to manage pseudoaneurysms by embolisation with radiological coils [3]
- Pseudoaneurysms are an ABSOLUTE contraindication to endoscopic drainage unless arterial embolisation is performed first [3]
- Why? Severe and fatal haemorrhage can occur following endoscopic drainage in patients with an unsuspected pseudoaneurysm [3]
Before draining ANY pancreatic fluid collection, always consider whether a pseudoaneurysm might be present. If the Hb is dropping, the collection is expanding, or there's unexplained GI bleeding — do angiography FIRST.
8. Prevention of Recurrence [3]
- Hypertriglyceridaemia: Fibrates, dietary modification, insulin infusion in acute setting
- Hypercalcaemia: Treat underlying hyperparathyroidism (parathyroidectomy)
- Alcohol: Absolute abstinence counselling
- Offending drugs: Discontinue causative medications
| Severity | Key Management Steps |
|---|---|
| Mild (uncomplicated) | Conservative: IV LR fluids, analgesia (tramadol/pethidine), early oral feeding, correct electrolytes, PPI. USG for aetiology. Index admission cholecystectomy if biliary. |
| Moderately severe | As above + closer monitoring + NG/NJ feeding if oral not tolerated. CT at 72–96h. ERCP if biliary with cholangitis. |
| Severe | ICU: organ support (ventilation, inotropes, HD), NJ feeding → TPN, IV carbapenem if infected necrosis, ERCP if biliary, monitor IAP. Step-up approach for infected necrosis. Delayed cholecystectomy. |
High Yield Summary
General: IV Lactated Ringer's (target UO ≥ 0.5 mL/kg/h), analgesia (tramadol/pethidine — AVOID morphine and NSAIDs), early enteral nutrition (NG/NJ preferred over TPN), PPI, correct electrolytes.
Antibiotics: NOT prophylactic. Give ONLY for: cholangitis (Augmentin), infected necrosis (IV carbapenem — imipenem/meropenem), or SIRS with infection evidence.
Biliary pancreatitis: ERCP within 24–72h if cholangitis/CBD stone + index admission cholecystectomy (mild) or delayed cholecystectomy (severe).
Infected necrosis: Step-up approach — antibiotics → percutaneous/endoscopic drainage → delayed necrosectomy (≥ 3–4 weeks). Minimally invasive preferred over open.
Pseudocyst: Observe 6 weeks; if > 5 cm and symptomatic → internal drainage (endoscopic cystogastrostomy preferred). If complicated → external drainage.
Pseudoaneurysm: Absolute contraindication to endoscopic drainage until angiographic embolisation performed first.
Lecture summary: (1) Conservative for uncomplicated, (2) Early ERCP + antibiotics for biliary pancreatitis with cholangitis, (3) IV carbapenem for necrotising pancreatitis, (4) Drainage of infected necrosis, (5) Cystogastrostomy for persistent large pseudocysts.
Active Recall - Management of Acute Pancreatitis
References
[2] Senior notes: maxim.md (Acute pancreatitis section) [3] Senior notes: felixlai.md (Acute pancreatitis section) [15] Lecture slides: Acute pancreatitis.pdf (p9 — Aim in treatment of acute pancreatitis) [16] Lecture slides: Acute pancreatitis.pdf (p50 — Summary) [17] Lecture slides: Acute pancreatitis.pdf (p12 — Principles of management of severe pancreatitis) [18] Lecture slides: Acute pancreatitis.pdf (p16 — Treatment protocol of acute biliary pancreatitis) [19] Lecture slides: Acute pancreatitis.pdf (p24 — Definitive treatment for infected pancreatic necrosis) [20] Lecture slides: Acute pancreatitis.pdf (p44/p49 — Treatment strategy for pancreatic pseudocyst)
Complications of Acute Pancreatitis
The lecture slide gives a powerful snapshot of the clinical course [21]:
Clinical course of acute pancreatitis (per 100 patients):
- 70 patients with uneventful recovery (Mild pancreatitis)
- 30 patients with complications
- 20 patients with prolonged hospital stay
- 10 patients died (Severe pancreatitis) [21]
So roughly 30% of patients develop complications, and the overall mortality is about 10%. This frames everything that follows — complications are common and can be lethal.
Definition of severe pancreatitis: pancreatitis associated with organ failure and/or local complications e.g. necrosis, abscess formation, or pseudocyst [14]
Complications are broadly divided into local (things happening in and around the pancreas) and systemic (distant organ effects driven by the cytokine storm). I will explain each from first principles, connecting back to the pathophysiology.
A. Local Complications
These arise because the pancreas sits in the retroperitoneum surrounded by vital structures (duodenum, CBD, splenic vessels, portal vein, SMA/SMV, colon, stomach). When autodigestion extends beyond the pancreas, it damages everything in its path.
Local complications of acute pancreatitis [22]:
- Pancreatic and/or peripancreatic necrosis and haemorrhage
- Pancreatic abscess
- Pseudocyst
- Gastric fistula
- Colonic fistula
- Duodenal fistula
- Duodenal obstruction
- Splenic vein thrombosis → left-sided portal hypertension
- SMV or SMA thrombosis → bowel infarction [22]
A1. Pancreatic Fluid Collections (Revised Atlanta Classification)
This is one of the most commonly tested topics. The key organising principle is a 2 × 2 matrix — based on (1) whether necrosis is present and (2) whether it's early (< 4 weeks) or late (≥ 4 weeks) [2][3]:
| Interstitial oedematous pancreatitis (No necrosis) | Necrotising pancreatitis (Necrosis present) | |
|---|---|---|
| < 4 weeks | Acute Peripancreatic Fluid Collection (APFC) | Acute Necrotic Collection (ANC) |
| ≥ 4 weeks | Pancreatic Pseudocyst | Walled-Off Necrosis (WON) |
- Timeline: Early complication developing < 4 weeks after onset [3]
- What it is: Enzyme-rich fluid that leaks from the inflamed pancreas into the peripancreatic spaces
- Key feature: Does NOT have a well-defined wall — the fluid simply collects in anatomical spaces (lesser sac, anterior pararenal space) [3]
- Imaging: Anechoic collection on USG; fluid-density collection without a capsule on CT
- Clinical significance: Usually remains asymptomatic and resolves spontaneously without the need for drainage [3]
- Management: Observation — resolves within 7–10 days [3]
Why does it resolve? The inflammatory exudate is reabsorbed by the peritoneum and lymphatics as the acute inflammation settles. Intervention would introduce infection risk into a sterile, self-resolving process.
"Pseudo" = false (Greek) — this is a "false cyst" because it lacks an epithelial lining (true cysts are lined by epithelium). It's walled by inflammatory fibrosis instead.
- Timeline: Late complication developing > 4 weeks after onset [3]
- Definition: Encapsulated collection of fluid with a well-defined inflammatory wall (without epithelial cells), usually outside the pancreas, with minimal or no necrosis [3]
- Pathophysiology: Pancreatic ductal disruption (partial or complete) → pancreatic juice leaks into the peripancreatic space → over weeks, the body walls off this fluid with granulation tissue and fibrosis → a defined "pseudocyst" forms
- Risk factors: Chronic pancreatitis > acute pancreatitis [2] — because ductal disruption is more common with chronic duct damage
- Clinical features [2]:
- Persistent epigastric pain — the collection causes pressure on surrounding structures
- Mass effect: gastric outlet obstruction (GOO — the pseudocyst compresses the stomach/duodenum), obstructive jaundice (compresses the CBD)
- Palpable epigastric mass on examination
- Investigations:
- Amylase persistently elevated [2] — because the pseudocyst communicates with the pancreatic duct, so enzyme-rich fluid continuously leaks
- CT abdomen with contrast: well-defined, homogeneous, fluid-density collection with a distinct enhancing wall; NO solid component (unlike WON)
- Management [3][20]:
- Observe — watchful waiting for 6 weeks to allow the wall to "mature" (thicken and become strong enough to hold sutures/stents). 50% resolve spontaneously [2].
- If cyst > 5 cm by 6 weeks → internal drainage [20]:
- If cyst develops complications (e.g. bleeding, rupture, infection, obstruction) → external drainage [20]
Pseudocyst vs WON — The Critical Distinction
A pseudocyst contains purely liquid (pancreatic juice) with NO necrotic debris. A WON contains solid necrotic material mixed with fluid. This distinction matters because pseudocysts can be drained with a simple stent, whereas WON may require necrosectomy (debridement of solid debris) in addition to drainage. CT or MRI can differentiate them — look for solid content within the collection.
- Timeline: Early complication developing < 4 weeks [3]
- Definition: Collection containing variable amounts of both fluid and necrosis associated with necrotising pancreatitis, with no defined wall [3]
- Content: Mix of semisolid and solid material — non-viable pancreatic parenchyma [2]
- Key feature: Necrosis can involve the pancreatic parenchyma or the peripancreatic tissues [3]
- Imaging: Heterogeneous collection on CT (mixture of fluid and non-enhancing solid tissue); no capsule
- Management: Usually conservative unless infected (see step-up approach in management section)
- Timeline: Late complication developing > 4 weeks [3]
- Definition: Mature and encapsulated collection of pancreatic or peripancreatic necrosis that has developed a well-defined inflammatory wall [3]
- Key feature: Contains solid necrotic debris within a wall — this is what distinguishes it from a pseudocyst
- Clinical features [2]:
- Mass effect: palpable mass, GOO, obstructive jaundice [2]
- Imaging: CT abdomen with contrast — well-defined wall, can be intra-pancreatic or extra-pancreatic [2]; heterogeneous content (solid + liquid)
- Management [2]:
This is the most feared local complication and the main driver of mortality.
- Definition: Inflammation associated with pancreatic parenchymal necrosis or peripancreatic necrosis [3]
- Pathophysiology: Two mechanisms converge:
- Diagnosis: Contrast-enhanced CT — necrotic areas show hypoenhancement (they have lost their blood supply and cannot take up contrast) [2]. Gas within necrotic areas on CT is suggestive of infected necrosis [3].
Sterile vs Infected Necrosis
| Sterile Necrosis | Infected Necrosis | |
|---|---|---|
| Frequency | More common initially | Occurs in 5–10% of cases [3]; typically develops in week 2–4 |
| Mechanism | Direct enzyme damage + ischaemia | Gut bacterial translocation (mucosal barrier breakdown → E. coli, Klebsiella → colonise necrotic tissue) |
| Diagnosis | Non-enhancing areas on CT; no gas | Gas in necrosis on CT; clinical deterioration; FNA is the gold standard for diagnosing infected necrosis but is rarely necessary since treatment is based on clinical status and blood culture [3] |
| Management | Conservative (supportive) unless symptomatic | Step-up approach: IV carbapenem → drainage → delayed necrosectomy |
Why Does Necrosis Get Infected?
Recall the pathophysiology: volume depletion → hypoperfusion of gut → mucosal barrier breakdown → bacterial translocation → endotoxaemia [9]. The bacteria (especially enteric Gram-negatives) seed into the avascular necrotic tissue, which has no blood supply to deliver immune cells or antibiotics. This is why: (1) carbapenems are chosen specifically for their ability to penetrate necrotic tissue, and (2) prevention of necrosis through aggressive fluid resuscitation is so critical.
A3. Peripancreatic Vascular Complications
The pancreas is surrounded by major vessels (splenic artery/vein, GDA, SMA/SMV, portal vein). Inflammation and enzyme leakage erode into these structures.
- Vessels affected: Splenic vein, portal vein, or superior mesenteric vein (SMV) [3]
- Mechanism: Inflammatory phlebitis — the inflamed pancreas directly irritates the adjacent vein wall → endothelial injury → thrombosis (Virchow's triad: endothelial damage + stasis from compression + hypercoagulability from inflammation)
- Consequences:
- Splenic vein thrombosis → left-sided (sinistral) portal hypertension [22] — this is a classic exam point. The splenic vein drains into the portal vein; when it's occluded, blood backs up through the short gastric veins → gastric fundal varices (NOT oesophageal varices, because the portal vein itself may be patent). Isolated gastric varices in a non-cirrhotic patient should prompt you to think of splenic vein thrombosis from pancreatitis.
- SMV or SMA thrombosis → bowel infarction [22] — compromise of bowel perfusion → mesenteric ischaemia → gangrene
- Portal vein thrombosis → hepatic decompensation [3]
- Management: Treatment should focus on the underlying pancreatitis as effective treatment may result in spontaneous resolution of thrombosis [3]. Anticoagulation is considered on a case-by-case basis (risk of haemorrhage in necrotic pancreatitis vs risk of bowel infarction from clot propagation).
"Pseudo" = false; "aneurysm" = dilation of a blood vessel. A pseudoaneurysm is NOT a true aneurysm (which involves all three vessel wall layers). It's a contained rupture — pancreatic enzymes (especially elastase) erode through the arterial wall, and blood is contained only by the adventitia and surrounding tissues.
- Frequency: Rare but serious complication, most common in patients with necrotising pancreatitis [3]
- Arteries commonly involved: Gastroduodenal artery (GDA), left gastric artery, and splenic artery [3] — these arteries run in close proximity to the pancreas
- Pancreatic pseudo-aneurysm: erosion into artery (especially GDA) [2]
- Danger: Rupture is a life-threatening emergency [3] — massive intra-abdominal or GI haemorrhage
- Three clinical features suggesting pseudoaneurysm [3]:
- Unexplained GI bleeding
- Drop in haemoglobin (Hb) or haematocrit
- Sudden expansion of a pancreatic fluid collection
- Diagnosis and Management: Angiography is the first step — both diagnostic and therapeutic [3] (can embolise with radiological coils)
- Critical safety rule: Pseudoaneurysms are an ABSOLUTE contraindication to endoscopic drainage unless arterial embolisation is performed first [3] — Severe and fatal haemorrhage can occur following endoscopic drainage in patients with an unsuspected pseudoaneurysm [3]
Activated enzymes erode through the walls of adjacent hollow viscera:
| Fistula Type | Mechanism | Clinical Consequence |
|---|---|---|
| Gastric fistula [22] | Enzyme erosion through the posterior gastric wall (which lies directly anterior to the pancreas) | GI bleeding, peritonitis |
| Colonic fistula [22] | Erosion into the transverse colon (which runs anterior to the pancreatic body) | Faeculent drainage, sepsis |
| Duodenal fistula [22] | Erosion into the C-loop of the duodenum (which cradles the pancreatic head) | Duodenal content leak, sepsis |
These are uncommon but severe complications, usually associated with necrotising pancreatitis. Management is typically conservative initially (NPO, TPN, drainage), with surgery reserved for failures.
- Duodenal obstruction [22] — the inflamed/necrotic pancreatic head or a pseudocyst compresses the duodenum (C-loop), causing gastric outlet obstruction
- Symptoms: persistent vomiting, inability to tolerate oral intake, gastric distension
- Management: NG decompression, treat underlying pancreatitis, endoscopic duodenal stenting if persistent, surgical bypass (gastrojejunostomy) rarely needed
- Mechanism: Complete disruption of the main pancreatic duct (from necrosis or trauma) → pancreatic juice leaks freely into the peritoneal cavity → pancreatic ascites
- Clinical features: Progressive abdominal distension, shifting dullness
- Diagnosis: Ascitic fluid amylase is massively elevated (typically > 1000 U/L); protein is usually > 25 g/L (exudative)
- Management: ERCP with pancreatic duct stenting to bridge the disruption; surgical repair if ERCP fails
When significant pancreatic parenchyma is destroyed:
| Insufficiency | Threshold | Clinical Features | Mechanism |
|---|---|---|---|
| Exocrine | < 10% of exocrine function remaining | Steatorrhoea (fatty, malodorous, floating stools), malnutrition, fat-soluble vitamin deficiency (A, D, E, K → night blindness, osteoporosis, coagulopathy) | Loss of acinar cells → inadequate production of lipase, amylase, proteases → maldigestion of fats, carbohydrates, proteins |
| Endocrine | Islet cell mass destruction | Diabetes mellitus (hyperglycaemia), also risk of hypoglycaemia | Loss of β-cells → insulin deficiency; loss of α-cells → glucagon deficiency (risk of brittle diabetes with hypoglycaemia) |
Exocrine Before Endocrine
The exocrine pancreas is more vulnerable than the endocrine pancreas. Acinar cells (exocrine) are destroyed first because they directly produce the enzymes causing autodigestion. The islets of Langerhans (endocrine) are more resistant to injury — they are scattered islands surrounded by connective tissue that provides some protection. This is why steatorrhoea develops before diabetes in the course of progressive pancreatic destruction.
Systemic complications are driven by the cytokine storm — the same NF-κB-dependent inflammatory cascade (TNF-α, IL-1, IL-6) that we discussed in pathophysiology. These cytokines enter the bloodstream and cause distant organ injury.
Systemic Complications of acute pancreatitis [23]:
- Heart failure
- Respiratory failure
- Renal failure
- Cholestasis
- DIC
- Hyperglycaemia
- Hypocalcaemia [23]
Let me explain each from first principles:
| Complication | Pathophysiology | Clinical Features | Management |
|---|---|---|---|
| Respiratory failure / ARDS [23][3] | Cytokines (TNF-α, IL-6) → pulmonary capillary endothelial damage → increased permeability → non-cardiogenic pulmonary oedema. Also: pleural effusions (transdiaphragmatic lymphatic drainage), diaphragmatic splinting from adjacent inflammation. Phospholipase A2 destroys surfactant. | Dyspnoea, hypoxaemia (PaO₂ < 60 mmHg), bilateral infiltrates on CXR, PaO₂/FiO₂ ≤ 300 | O₂ supplementation → mechanical ventilation; PEEP; lung-protective ventilation strategy |
| Heart failure [23][3] | (1) Myocardial depressant factors (TNF-α, IL-1 directly depress myocardial contractility). (2) High-output failure from SIRS-driven vasodilation. (3) Hypovolaemia → cardiogenic shock in severe cases. | Hypotension, tachycardia, elevated CVP, pulmonary oedema | Fluid resuscitation, inotropes (dobutamine), vasopressors (noradrenaline) |
| Renal failure / AKI [23][3] | (1) Prerenal: hypovolaemia from massive third-spacing → reduced renal perfusion. (2) Intrinsic: cytokine-mediated tubular injury, myoglobinuria if compartment syndrome develops. (3) Abdominal compartment syndrome → renal vein compression. | Oliguria, rising creatinine/BUN, metabolic acidosis | Aggressive IV fluids; if refractory → haemodialysis [2] |
| DIC [23][2] | Massive tissue damage → release of tissue factor → systemic activation of coagulation cascade → consumption of clotting factors and platelets → paradoxical bleeding AND thrombosis. "Disseminated" = widespread, "Intravascular" = inside vessels, "Coagulation" = clotting. | Bleeding from puncture sites, petechiae, oozing; lab: ↑PT/APTT, ↓fibrinogen, ↑D-dimer, ↓platelets, schistocytes on film | Treat the underlying cause (pancreatitis); supportive: FFP, cryoprecipitate, platelet transfusion |
| Cholestasis [23] | Oedema of the pancreatic head compresses the intrapancreatic portion of the CBD → obstructive jaundice | Jaundice, dark urine, pale stools, ↑ALP/GGT/conjugated bilirubin | Usually resolves as pancreatic oedema settles; ERCP if persistent |
| Hyperglycaemia [23][3] | Islet cell damage (β-cell destruction → insulin deficiency) + stress response (cortisol, glucagon, catecholamines → counter-regulatory hyperglycaemia) | Polyuria, polydipsia, elevated blood glucose; may progress to DKA or HHS | Insulin (sliding scale or infusion); avoid over-correction |
| Hypocalcaemia [23][3] | (1) Fat saponification — lipase causes fat necrosis → released fatty acids bind calcium → insoluble calcium soaps. (2) Hypoalbuminaemia from third-spacing → reduced total (but not necessarily ionised) calcium. (3) Possible ↓PTH response. | Tetany (Chvostek's sign, Trousseau's sign), perioral paraesthesia, prolonged QTc → risk of arrhythmia | IV calcium gluconate (10 mL of 10% solution); monitor ionised calcium and ECG |
Additional systemic complications [3]:
| Complication | Pathophysiology |
|---|---|
| Paralytic ileus [3] | Retroperitoneal inflammation → reflex inhibition of peristalsis via splanchnic nerves. The bowel "shuts down" as a protective mechanism. |
| Abdominal compartment syndrome [3][2] | Massive retroperitoneal oedema + ascites + ileus → markedly elevated intra-abdominal pressure (IAP > 20 mmHg with new organ failure) → compresses IVC (↓venous return → shock), renal veins (↓renal perfusion → AKI), diaphragm (↓ventilation → respiratory failure). A devastating complication requiring measurement of IAP [2] and potentially decompressive laparotomy. |
| Retroperitoneal bleeding [3] | Elastase erosion of retroperitoneal blood vessels → haemorrhage tracking to produce Cullen's/Grey Turner's/Fox's signs |
Systemic inflammatory response syndrome (SIRS) — Pancreatic inflammation results in activation of a cytokine cascade that manifests clinically as SIRS [3]
The connection from local pancreatic inflammation to systemic organ failure:
Organ failure may present as shock, acute respiratory failure, and renal failure [3]
The Modified Marshall Score defines organ failure (score ≥ 2 in any system):
- Respiratory: PaO₂/FiO₂ ≤ 300
- Cardiovascular: SBP < 90 mmHg not responding to fluids
- Renal: Creatinine ≥ 170 μmol/L
Persistent organ failure ( > 48 hours) = severe pancreatitis = 15–40% mortality.
Understanding the timeline helps predict what complication to expect and when:
| Time | Phase | Complications |
|---|---|---|
| Days 1–7 | Early inflammatory phase | SIRS, organ failure (ARDS, AKI, shock), APFC, ANC, paralytic ileus, electrolyte derangement (hypocalcaemia, hyperglycaemia) |
| Weeks 2–4 | Transitional phase | Infected necrosis (peak incidence weeks 2–4 from bacterial translocation), persistent organ failure, splanchnic venous thrombosis, pseudoaneurysm |
| > 4 weeks | Late phase | Pseudocyst, WON, chronic pancreatic insufficiency (exocrine → endocrine), pancreatic duct stricture, fistulae |
The Two Peaks of Mortality in Acute Pancreatitis
Early mortality (week 1): Driven by SIRS and multi-organ failure from the cytokine storm — this is "sterile" and cannot be prevented by antibiotics. Late mortality (weeks 2–6): Driven by infected necrosis and sepsis from bacterial translocation — this is where antibiotics (carbapenems) and the step-up approach play their role. Understanding these two distinct mortality peaks explains why the management approach differs in the early vs late phases.
Even after recovery from acute pancreatitis, patients are at risk of:
| Sequela | Mechanism | Prevention |
|---|---|---|
| Recurrent pancreatitis | Untreated aetiology (persistent gallstones, ongoing alcohol use) | Cholecystectomy for gallstone pancreatitis; alcohol abstinence counselling |
| Chronic pancreatitis | Repeated episodes of acute inflammation → fibrosis → ductal changes → calcification | Alcohol cessation; smoking cessation |
| Pancreatic cancer | Chronic inflammation is a risk factor for pancreatic ductal adenocarcinoma (2% lifetime risk with chronic pancreatitis) | Surveillance in high-risk patients; smoking/alcohol cessation |
| Diabetes mellitus | Permanent β-cell destruction from necrosis | Monitor blood glucose long-term; insulin as needed |
High Yield Summary
Local complications (Revised Atlanta classification of fluid collections):
- < 4 weeks, no necrosis: APFC → observe (resolves in 7–10 days)
- < 4 weeks, necrosis: ANC → conservative unless infected
- ≥ 4 weeks, no necrosis: Pseudocyst → observe 6 weeks, drain if > 5 cm and symptomatic (cystogastrostomy)
- ≥ 4 weeks, necrosis: WON → EUS-guided drainage ± necrosectomy
Vascular complications:
- Splenic vein thrombosis → left-sided portal hypertension (isolated gastric varices)
- SMV/SMA thrombosis → bowel infarction
- Pseudoaneurysm (GDA, splenic, left gastric) → ABSOLUTE contraindication to drainage until embolised
Infected necrosis (5–10%): gas on CT is suggestive; step-up approach (antibiotics → drainage → delayed necrosectomy)
Systemic complications (from cytokine storm): ARDS, heart failure, renal failure, DIC, cholestasis, hyperglycaemia, hypocalcaemia
Two mortality peaks: Early (week 1) = SIRS/organ failure; Late (weeks 2–6) = infected necrosis/sepsis
Fistulae: gastric, colonic, duodenal — from enzyme erosion into adjacent hollow viscera
Long-term: risk of chronic pancreatitis, diabetes, pancreatic cancer
Active Recall - Complications of Acute Pancreatitis
References
[2] Senior notes: maxim.md (Acute pancreatitis section) [3] Senior notes: felixlai.md (Acute pancreatitis section) [9] Lecture slides: Acute pancreatitis.pdf (p6 — Acute oedematous pancreatitis progression) [10] Lecture slides: Acute pancreatitis.pdf (p7 — Reasons for progression to necrotising pancreatitis) [14] Lecture slides: Acute pancreatitis.pdf (p11 — Definition of severe pancreatitis) [20] Lecture slides: Acute pancreatitis.pdf (p44/p49 — Treatment strategy for pancreatic pseudocyst) [21] Lecture slides: Acute pancreatitis.pdf (p2 — Clinical course of acute pancreatitis) [22] Lecture slides: Acute pancreatitis.pdf (p18 — Local complications of acute pancreatitis) [23] Lecture slides: Acute pancreatitis.pdf (p19 — Systemic complications of acute pancreatitis)
High Yield Summary
Definition: Acute inflammation of pancreatic parenchyma from premature intracellular activation of trypsinogen → autodigestion.
Aetiology: Gallstones (55%) > Alcohol (35%) > Miscellaneous (10%) — GAME ID mnemonic.
Pathophysiology: Enzyme activation → autodigestion → pancreatic/peripancreatic necrosis → cytokine storm (NF-κB, TNF-α, IL-6) → SIRS → organ failure. Volume depletion → pancreatic hypoperfusion → progression to necrotising pancreatitis.
Classification (Revised Atlanta):
- Morphology: Interstitial oedematous vs. Necrotising
- Severity: Mild (no organ failure) → Moderately severe (transient OF < 48h or local complications) → Severe (persistent OF > 48h)
Scoring: Ranson's (GALAW + CHOBBS, ≥ 3 = severe, needs 48h), APACHE II (≥ 8 = severe, can calculate daily), Glasgow (≥ 3/8), CRP > 150 at 48h, BISAP.
Clinical features: Epigastric pain radiating to back (retroperitoneal), relieved by leaning forward, N/V, fever. Signs: Cullen's (periumbilical ecchymosis), Grey Turner's (flank ecchymosis), Fox's (inguinal ecchymosis) = haemorrhagic pancreatitis. Tetany from hypocalcaemia (fat saponification).
Diagnosis: 2/3 of — (1) Typical pain, (2) Amylase/lipase ≥ 3× ULN, (3) Imaging findings.
High Yield Summary
DDx of acute pancreatitis = DDx of acute epigastric pain. The major differentials from the notes and slides are:
- Peptic ulcer disease / PPU — CXR for pneumoperitoneum; PPU causes false-positive amylase
- Choledocholithiasis / Cholangitis / Cholecystitis — cholestatic LFTs, Murphy's sign, USG
- Hepatitis — massively elevated transaminases, viral serology
- Mesenteric ischaemia — pain out of proportion, AF patient, CT angiography
- Intestinal obstruction — colicky pain, absolute constipation, dilated loops on AXR
- Myocardial infarction — ECG + troponin must be checked in ALL patients with epigastric pain
- Ruptured AAA — pulsatile mass, hypotension, retroperitoneal haemorrhage (same Cullen's/Grey Turner's)
- DKA — glucose, ketones, ABG
Key principle: Serum lipase is more specific than amylase for pancreatitis. Always check CXR (to exclude PPU), ECG + troponin (to exclude MI), and consider CT with contrast when the diagnosis is uncertain.
High Yield Summary
Diagnostic Criteria (Revised Atlanta): 2 out of 3 — (1) Typical epigastric pain radiating to back, (2) Amylase or lipase ≥ 3× ULN, (3) Characteristic imaging findings.
Pancreatic Enzymes: Lipase is superior to amylase — more sensitive (especially alcoholic), more specific, rises earlier, lasts longer. Neither correlates with severity.
False positive amylase: PPU, ruptured AAA, DKA, macroamylasaemia, bowel ischaemia.
USG abdomen: First-line imaging — primarily to identify gallstones as the aetiology. Pancreas only seen ~50% of the time.
CT abdomen with contrast: Gold standard (Sn 90%, Sp 100%). Contrast essential to detect necrosis (hypoenhancement). Best at 72–96 hours. Gas in necrosis = infected necrosis.
AXR signs: Sentinel loop sign (localised ileus), colonic cut-off sign (descending colon spasm), obliteration of psoas outline (retroperitoneal fluid).
Severity assessment: Ranson's (GALAW + CHOBBS, ≥ 3 = severe, needs 48h), APACHE II (≥ 8, can calculate daily), CRP > 150 at 48h, Balthazar CTSI (grade 0–4 + necrosis 0–6), Modified Marshall Score for organ failure.
Always check: ECG + troponin (exclude MI), CXR (exclude PPU).
High Yield Summary
General: IV Lactated Ringer's (target UO ≥ 0.5 mL/kg/h), analgesia (tramadol/pethidine — AVOID morphine and NSAIDs), early enteral nutrition (NG/NJ preferred over TPN), PPI, correct electrolytes.
Antibiotics: NOT prophylactic. Give ONLY for: cholangitis (Augmentin), infected necrosis (IV carbapenem — imipenem/meropenem), or SIRS with infection evidence.
Biliary pancreatitis: ERCP within 24–72h if cholangitis/CBD stone + index admission cholecystectomy (mild) or delayed cholecystectomy (severe).
Infected necrosis: Step-up approach — antibiotics → percutaneous/endoscopic drainage → delayed necrosectomy (≥ 3–4 weeks). Minimally invasive preferred over open.
Pseudocyst: Observe 6 weeks; if > 5 cm and symptomatic → internal drainage (endoscopic cystogastrostomy preferred). If complicated → external drainage.
Pseudoaneurysm: Absolute contraindication to endoscopic drainage until angiographic embolisation performed first.
Lecture summary: (1) Conservative for uncomplicated, (2) Early ERCP + antibiotics for biliary pancreatitis with cholangitis, (3) IV carbapenem for necrotising pancreatitis, (4) Drainage of infected necrosis, (5) Cystogastrostomy for persistent large pseudocysts.
High Yield Summary
Local complications (Revised Atlanta classification of fluid collections):
- < 4 weeks, no necrosis: APFC → observe (resolves in 7–10 days)
- < 4 weeks, necrosis: ANC → conservative unless infected
- ≥ 4 weeks, no necrosis: Pseudocyst → observe 6 weeks, drain if > 5 cm and symptomatic (cystogastrostomy)
- ≥ 4 weeks, necrosis: WON → EUS-guided drainage ± necrosectomy
Vascular complications:
- Splenic vein thrombosis → left-sided portal hypertension (isolated gastric varices)
- SMV/SMA thrombosis → bowel infarction
- Pseudoaneurysm (GDA, splenic, left gastric) → ABSOLUTE contraindication to drainage until embolised
Infected necrosis (5–10%): gas on CT is suggestive; step-up approach (antibiotics → drainage → delayed necrosectomy)
Systemic complications (from cytokine storm): ARDS, heart failure, renal failure, DIC, cholestasis, hyperglycaemia, hypocalcaemia
Two mortality peaks: Early (week 1) = SIRS/organ failure; Late (weeks 2–6) = infected necrosis/sepsis
Fistulae: gastric, colonic, duodenal — from enzyme erosion into adjacent hollow viscera
Long-term: risk of chronic pancreatitis, diabetes, pancreatic cancer
Acute Cholecystitis
Acute inflammation of the gallbladder, most commonly caused by obstruction of the cystic duct by gallstones, leading to distension, ischemia, and potential infection.
Biliary Cysts
Biliary cysts are congenital cystic dilatations of the intrahepatic and/or extrahepatic bile ducts that predispose to cholangitis, stone formation, and cholangiocarcinoma.