Mirizzi Syndrome

1. Definition

Mirizzi syndrome is defined as obstruction of the common hepatic duct (CHD) caused by extrinsic compression from an impacted gallstone in the cystic duct or Hartmann's pouch (infundibulum) of the gallbladder ^[1][2]. The name tells you the core pathology: a gallstone that's not inside the common bile duct (CBD), but beside it, pushing on it from the outside.

The key conceptual distinction: this is extrinsic compression — the stone is in the gallbladder/cystic duct, not in the CBD itself, yet it still causes obstructive jaundice. This is what makes it a diagnostic trap.

As chronic inflammation persists, the impacted stone can erode through the wall of the cystic duct/gallbladder into the adjacent bile duct, creating a cholecystobiliary fistula (an abnormal communication between gallbladder and the common hepatic duct or CBD) ^[1][2]. This fistula is the basis for the classification system and dictates surgical approach.

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2. Epidemiology

Why the female predominance? Because Mirizzi syndrome is a complication of gallstones, and gallstones are far more common in women — remember the 5Fs: Female, Fat, Forty, Fertile, Family history ^[1]. More gallstones → more chance of impaction at Hartmann's pouch → more Mirizzi syndrome.

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3. Risk Factors

Since Mirizzi syndrome is fundamentally a complication of gallstone disease, the risk factors are those for cholelithiasis, plus anatomical factors that predispose to the specific impaction pattern:

3a. Risk Factors for Gallstone Formation (upstream cause)

• 5Fs: Female, Forty (middle age), Fat (obesity), Fertile (pregnancy/multiparity), Family history ^[1]
• Rapid weight loss (e.g., post-bariatric surgery) — increases biliary cholesterol saturation
• Diabetes mellitus
• Liver cirrhosis
• Haemolytic disorders (thalassaemia, hereditary spherocytosis, sickle cell disease) — excess bilirubin → pigment stones
• Drugs: oral contraceptives, estrogen replacement therapy — increase biliary cholesterol secretion
• Crohn's disease (terminal ileal disease → impaired bile salt reabsorption → altered bile composition)
• Total parenteral nutrition (TPN) — gallbladder stasis

3b. Anatomical Risk Factors Specific to Mirizzi Syndrome

• Low insertion of the cystic duct — when the cystic duct runs parallel to and closely alongside the CHD for a long distance, an impacted stone in the cystic duct is more likely to compress the CHD
• Long cystic duct running parallel to the CHD
• Large gallstones — stones > 1 cm are more likely to impact at Hartmann's pouch and are large enough to exert significant extrinsic compression
• Chronic cholecystitis with recurrent inflammation — leads to fibrosis and adhesions that "fix" the gallbladder to the bile duct, facilitating compression and eventual fistula formation

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4. Anatomy and Function

Understanding Mirizzi syndrome requires a solid grasp of biliary anatomy:

4a. Gallbladder Anatomy

The gallbladder is a pear-shaped hollow organ on the inferior surface of the liver (segments IV and V). It has four anatomical parts ^[1]:

1. Fundus — the blind end, projects beyond the inferior liver edge at the tip of the 9th costal cartilage (transpyloric plane landmark)
2. Body — the main portion, lying in the gallbladder fossa
3. Infundibulum (Hartmann's pouch) — a saccular outpouching at the junction of the body and neck; the convexity of the curved neck. This is where stones classically impact in Mirizzi syndrome ^[1][2]
4. Neck — the narrow tapered portion leading to the cystic duct; contains the spiral valves of Heister

4b. The Cystic Duct and Its Relation to the CHD

• The cystic duct (typically 2–4 cm long) connects the gallbladder neck to the common hepatic duct
• The CHD is formed by the confluence of the right and left hepatic ducts at the hilum (porta hepatis)
• The cystic duct joins the CHD (usually on its lateral aspect) to form the common bile duct (CBD)
• Calot's triangle (cystohepatic triangle): bounded by the cystic duct inferiorly, common hepatic duct medially, and inferior liver edge superiorly. Contains the cystic artery (branch of right hepatic artery) and the cystic lymph node (of Lund). This is the critical dissection zone in cholecystectomy — and in Mirizzi syndrome, it is obliterated by inflammation and fibrosis, making surgery treacherous.

4c. The "Compression Zone"

The proximity of Hartmann's pouch/cystic duct to the common hepatic duct is the anatomical basis for Mirizzi syndrome. When a large stone impacts in this region, it compresses the CHD from the lateral or anterolateral aspect. The closer these structures are anatomically (particularly with a long parallel cystic duct), the easier it is for a stone to cause obstruction.

4d. Function

• The gallbladder concentrates and stores bile (up to 10-fold concentration) between meals
• Upon fatty meal ingestion → CCK release from duodenal I-cells → gallbladder contraction + sphincter of Oddi relaxation → bile ejection into duodenum
• In Mirizzi syndrome, gallbladder function is typically already impaired by chronic stone disease and inflammation

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5. Etiology (Focused on Hong Kong Context)

5a. Primary Cause

Cholelithiasis is the overwhelmingly dominant cause. Mirizzi syndrome is essentially always caused by gallstones — specifically, large stones (often > 1–2 cm) impacted in Hartmann's pouch or the cystic duct ^[1][2].

5b. Types of Gallstones in Hong Kong

In the Hong Kong context, recurrent pyogenic cholangitis (RPC) is an important associated condition. RPC (also called "Oriental cholangiohepatitis" or "Hong Kong disease") involves recurrent formation of brown pigment stones within intrahepatic ducts ^[1]. While RPC stones typically form within bile ducts (de novo), the chronic biliary inflammation and stone burden can contribute to gallbladder stone formation and, rarely, Mirizzi syndrome.

Parasitic infections relevant to Hong Kong and Southeast Asia that predispose to biliary stone disease include ^[1]:

• Clonorchis sinensis (Chinese liver fluke) — endemic in southern China, including Hong Kong
• Opisthorchis viverrini
• Ascaris lumbricoides

These parasites cause biliary inflammation, stasis, and serve as nidi for stone formation.

5c. Rare Causes of "Mirizzi-like" Syndrome

While classic Mirizzi syndrome is stone-related, extrinsic CHD compression can rarely be caused by:

• Gallbladder tumour (gallbladder carcinoma at the neck)
• Xanthogranulomatous cholecystitis
• Large parasitic cysts

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6. Pathophysiology

This is the heart of understanding the condition. The pathophysiology proceeds in a stepwise fashion:

Step 1: Stone Impaction

A large gallstone migrates into or forms within Hartmann's pouch or the proximal cystic duct. The stone becomes impacted — it cannot pass distally through the cystic duct (too large) and cannot fall back into the gallbladder body. This is the initiating event.

Why Hartmann's pouch? Because it is a natural "trap" — the pouch-like outpouching at the gallbladder neck creates a pocket where stones can lodge. The spiral valves of Heister in the cystic duct further prevent passage.

Step 2: Extrinsic Compression of the CHD

Due to the anatomical proximity of Hartmann's pouch/cystic duct to the CHD, the impacted stone exerts direct mechanical compression on the CHD from outside ^[1][2]. This causes:

• Partial or complete obstruction of bile flow through the CHD
• Dilatation of intrahepatic bile ducts proximal to the obstruction
• Normal-calibre CBD distal to the obstruction (below the level of cystic duct insertion)

This creates the characteristic imaging finding: dilated biliary system above the level of the gallbladder neck with an abrupt transition to normal-calibre CBD below ^[1].

Step 3: Secondary Inflammation and Cholangitis

The impacted stone and obstructed bile flow trigger:

• Local inflammatory response — pericholecystic inflammation, oedema, fibrosis
• Bile stasis proximal to obstruction → bacterial colonization → ascending cholangitis
• Recurrent episodes of cholangitis further exacerbate inflammation

Why does bile stasis predispose to infection? Normally, bile flow is sterile and the continuous antegrade flow "flushes" bacteria. When flow is obstructed, bacteria (normally present in small numbers from the duodenum via the sphincter of Oddi) multiply in the stagnant bile. The most common organisms are enteric Gram-negatives: E. coli, Klebsiella, and anaerobes ^[1].

Step 4: Cholecystobiliary Fistula Formation (Types II–IV/V)

With chronic inflammation and pressure necrosis, the impacted stone can:

• Erode through the wall of the cystic duct/gallbladder and the adjacent wall of the CHD/CBD
• Create an internal fistula between the gallbladder and the bile duct — the cholecystobiliary fistula (or "cholecystohepatic" / "cholecystocholedochal" fistula) ^[1][2]

Why does this happen? The stone sits pressed against the bile duct wall for weeks to months. Constant pressure + inflammatory mediators + ischaemia of the compressed wall → pressure necrosis → wall breakdown → fistula. This is the same mechanism by which a gallstone can erode into the duodenum (creating a cholecystoenteric fistula in gallstone ileus).

The extent of bile duct wall destruction determines the Csendes classification type (see below).

Step 5: Complications Cascade

Once the fistula is established:

• Gallstones can migrate through the fistula into the CBD → choledocholithiasis
• Chronic inflammation + biliary stasis → predispose to gallbladder carcinoma ^[1][2]
• Cholecystoenteric fistula may also form (Type V) → gallstone ileus if stone passes into bowel ^[2]

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7. Classification: Csendes Classification (Modified)

The Csendes classification (1989, updated by Csendes and Beltran 2008) is the standard classification system. It is based on the presence, size, and extent of the cholecystobiliary fistula, which directly determines the surgical approach ^[1][2].

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8. Clinical Features

Mirizzi syndrome has a variable clinical presentation ^[2], which is one reason it is frequently diagnosed late (often intraoperatively). The presentation depends on whether the patient has acute cholecystitis, cholangitis, or chronic biliary symptoms.

8a. Symptoms

8b. Signs

8c. Associated Presentations

Up to 1/3 of patients with Mirizzi syndrome present with concurrent acute cholecystitis ^[1], and in rare cases, acute pancreatitis ^[1] (if a stone also obstructs the pancreatic duct or ampulla).

There is an important association with gallbladder cancer ^[1][2][3]:

• The chronic inflammation, biliary stasis, and repeated mucosal injury predispose to dysplasia-carcinoma sequence
• Incidence of concurrent gallbladder carcinoma in Mirizzi syndrome is reported as 5–28% in various series
• This is why CT abdomen with contrast should be performed to look for enlarged porta hepatis lymph nodes or hepatic infiltration of metastasis ^[1]

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9. Key Pathophysiological Consequences of Obstructive Jaundice in Mirizzi Syndrome

These are the systemic effects of biliary obstruction that apply to any cause of obstructive jaundice but are directly relevant to Mirizzi syndrome management ^[3]:

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10. Summary of Clinical Approach (Pre-Diagnostic Framework)

Before diving into investigations (which will be covered in the next section), the clinical approach to a suspected Mirizzi syndrome patient follows this logic:

1. Suspect it when you see obstructive jaundice + gallstones + features that don't quite fit choledocholithiasis (e.g., imaging shows dilated intrahepatic ducts but no stone in the CBD, or a contracted/inflamed gallbladder with stone at the neck)
2. Assess severity: Is there cholangitis? (Charcot's/Reynolds') → this determines urgency of biliary decompression
3. Rule out malignancy: The overlap between Mirizzi syndrome and gallbladder cancer / cholangiocarcinoma is significant — CT is essential
4. Classify: The Csendes type determines the surgical approach — this is usually determined by ERCP and/or intraoperative findings

High Yield: Mirizzi syndrome is a "great mimicker" — it can present like acute cholecystitis, acute cholangitis, choledocholithiasis, or even biliary malignancy. The diagnosis is often made intraoperatively. Preoperative recognition is critical because it changes the surgical plan and reduces the risk of bile duct injury during cholecystectomy.

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Active Recall - Mirizzi Syndrome (Definition, Epidemiology, Pathophysiology, Classification, Clinical Features)

1. Define Mirizzi syndrome and explain why it is an exception to Courvoisier's Law.

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Mirizzi syndrome = CHD obstruction by extrinsic compression from an impacted stone in Hartmann's pouch or cystic duct. Exception to Courvoisier's Law because: the stone is at the GB neck (not in the CBD) so the GB body/fundus can still distend, giving jaundice with a palpable GB from a stone-related cause (whereas Courvoisier's Law states that in painless jaundice with palpable GB, the cause is unlikely to be stones).

2. Describe the stepwise pathophysiology from stone impaction to cholecystobiliary fistula formation.

Your answer

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1. Large stone impacts in Hartmann's pouch/cystic duct. 2. Extrinsic compression of CHD due to anatomical proximity. 3. Bile stasis and intrahepatic duct dilatation. 4. Recurrent cholangitis from bacterial colonisation of stagnant bile. 5. Chronic inflammation and pressure necrosis of the bile duct wall. 6. Erosion through the bile duct wall creates a cholecystobiliary fistula.

3. List the Csendes classification types (I-V) and the key distinguishing feature for each.

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Type I: No fistula, extrinsic compression only. Type II: Fistula involving less than 1/3 of CBD circumference. Type III: Fistula involving 1/3 to 2/3 of CBD circumference. Type IV: Fistula involving more than 2/3 (complete destruction) of CBD wall. Type V: Any type plus cholecystoenteric fistula (5A without gallstone ileus, 5B with gallstone ileus).

4. Why does Mirizzi syndrome predispose to gallbladder carcinoma?

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Chronic inflammation from the impacted stone, recurrent cholangitis, and biliary stasis cause repeated mucosal injury and regeneration, predisposing to dysplasia-carcinoma sequence. Incidence of concurrent gallbladder CA in Mirizzi syndrome is 5-28%.

5. Explain the pathophysiological basis for bleeding tendency in Mirizzi syndrome.

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Obstructive jaundice reduces bile salts reaching the gut. Bile salts are required for absorption of fat-soluble vitamins including vitamin K. Vitamin K is a cofactor for hepatic synthesis of clotting factors II, VII, IX, and X. Deficiency of these factors leads to coagulopathy and bleeding tendency.

6. What characteristic imaging finding on USG suggests Mirizzi syndrome rather than choledocholithiasis?

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Dilated biliary system above the level of the gallbladder neck (intrahepatic duct dilatation), with a stone impacted in the gallbladder neck/Hartmann's pouch, and an abrupt change to normal-calibre CBD below the level of the stone. In choledocholithiasis, you would expect a dilated CBD with a stone within it.

References

^[1] Senior notes: felixlai.md (Mirizzi syndrome, pp. 572–575; Cholelithiasis, p. 508; Gallbladder cancer etiology, p. 563; Obstructive jaundice, pp. 500–501; Recurrent pyogenic cholangitis, p. 526) ^[2] Senior notes: maxim.md (Mirizzi syndrome, pp. 130–132; Courvoisier's Law, p. 130; Gallstone ileus, p. 132; Obstructive jaundice, p. 251) ^[3] Lecture slides: Malignant biliary obstruction.pdf (Manifestations of pathophysiological disturbance of MBO: bleeding tendency, infection, poor wound healing)

Differential Diagnosis of Mirizzi Syndrome

Conceptual Framework: Why is the DDx Challenging?

The fundamental difficulty with Mirizzi syndrome is that it presents as obstructive jaundice ± cholangitis ± cholecystitis — a constellation shared by many hepatobiliary conditions. The stone is not in the CBD (where you'd expect it in choledocholithiasis), but its effects mimic a CBD stone. Additionally, the pericholecystic inflammation can mimic a hilar mass (gallbladder carcinoma, Klatskin tumour). This is why Mirizzi syndrome is frequently diagnosed only intraoperatively ^[1].

The DDx can be approached systematically by:

1. Level of biliary obstruction (hilar vs. mid-CBD vs. distal CBD) ^[3]
2. Mechanism of obstruction (intraluminal vs. mural vs. extramural) ^[4]
3. Clinical presentation pattern (cholangitis-predominant vs. cholecystitis-predominant vs. painless jaundice)

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Approach 1: DDx by Level of Obstruction

Mirizzi syndrome causes obstruction at the hilum / proximal CHD level — the stone in Hartmann's pouch compresses the CHD just below the hepatic confluence. This means the DDx is primarily against other causes of hilar-level obstruction ^[1][3].

Causes according to level of obstruction ^[3]:

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Approach 2: DDx by Mechanism of Obstruction

Differential diagnosis of obstructive jaundice ^[4]:

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Approach 3: Individual Differential Diagnoses with Distinguishing Features

These are the key conditions listed in the senior notes that must be systematically differentiated from Mirizzi syndrome ^[1]:

1. Choledocholithiasis (CBD Stones)

The most important differential — and the condition Mirizzi syndrome is most frequently confused with.

• Mechanism: Gallstone migrates from gallbladder through cystic duct and lodges within the CBD lumen ^[2][5]
• Why it mimics Mirizzi: Both cause obstructive jaundice, RUQ pain, and cholestatic LFTs. Both are stone-related. Both may present with Charcot's triad if complicated by cholangitis.
• How to distinguish:

2. Acute Cholecystitis

• Mechanism: Prolonged gallstone impaction at Hartmann's pouch/cystic duct → gallbladder distension → chemical then bacterial inflammation ^[6][7]
• Why it mimics Mirizzi: Both involve stone impaction at the same anatomical site (Hartmann's pouch/cystic duct). Both cause RUQ pain, fever, positive Murphy's sign. In fact, up to 1/3 of Mirizzi syndrome patients present with acute cholecystitis ^[1].
• How to distinguish:

Clinical pearl: If you see a patient with what looks like acute cholecystitis but with disproportionately significant jaundice and dilated intrahepatic ducts, think Mirizzi syndrome. "Severe jaundice is suggestive of cholangitis, CBD obstruction or obstruction of the bile ducts by severe pericholecystic inflammation or Mirizzi syndrome" ^[8].

3. Gallbladder Carcinoma (CA Gallbladder)

• Mechanism: Malignant neoplasm of the gallbladder (90% adenocarcinoma), often arising in a background of chronic cholecystitis/cholelithiasis ^[9]
• Why it mimics Mirizzi: Both can present with obstructive jaundice at the hilar level ^[3]. Both are associated with gallstones. The inflammatory mass in Mirizzi can look exactly like a gallbladder tumour on imaging. Critically, Mirizzi syndrome itself is a risk factor for gallbladder carcinoma — the two can coexist ^[1][2].
• How to distinguish:

4. Klatskin's Tumour (Hilar Cholangiocarcinoma)

• Mechanism: Cholangiocarcinoma (adenocarcinoma, > 90%) arising at the confluence of the hepatic ducts — "Klatskin" = perihilar cholangiocarcinoma ^[3][10]
• Why it mimics Mirizzi: Both cause hilar-level obstruction with intrahepatic duct dilatation. Both cause obstructive jaundice.
• How to distinguish:

5. Recurrent Pyogenic Cholangitis (RPC)

• Mechanism: Recurrent cholangitis from de novo intrahepatic pigment stone formation → stricturing and dilatation of the intrahepatic biliary tree ^[11]
• Why it mimics Mirizzi: Both cause cholangitis (Charcot's triad), both involve stones, and RPC is also an exception to Courvoisier's Law ^[2]. Both are common in the Hong Kong population.
• How to distinguish:

6. Liver Abscess

• Mechanism: Pyogenic (usually from biliary source or portal pyaemia) or amoebic abscess
• Why it mimics Mirizzi: Both cause fever, RUQ pain, and leukocytosis. A large abscess near the porta hepatis could compress the bile ducts.
• How to distinguish: USG/CT shows a fluid collection within the liver parenchyma (not a stone at GB neck). No intrahepatic duct dilatation pattern characteristic of biliary obstruction unless the abscess itself compresses ducts. Blood cultures/aspirate culture positive for organisms.

7. Infected Choledochal Cysts

• Mechanism: Congenital dilatation of biliary tree → bile stasis → infection ^[12]
• Why it mimics Mirizzi: Both cause RUQ pain, jaundice, and fever. Choledochal cysts can present with a palpable mass.
• How to distinguish: Diagnosed predominantly before age 10 (60%) ^[12]. USG/MRCP shows a cystic dilatation of the bile duct rather than a stone at GB neck. Classic triad of RUQ mass + pain + jaundice (though only present in minority of adults).

8. Acute Pancreatitis

• Mechanism: Premature activation of pancreatic enzymes → autodigestion ^[13]
• Why it mimics Mirizzi: Both can be caused by gallstones. Both cause RUQ/epigastric pain. Both elevate LFTs.
• How to distinguish: Pain in pancreatitis radiates to the back and is relieved by sitting up/leaning forward ^[13]. Markedly elevated serum amylase/lipase ( > 3× upper limit of normal). Pancreatic inflammation on CT. In Mirizzi, amylase may be mildly elevated but not to the degree seen in pancreatitis.

9. Acute Appendicitis

• Mechanism: Appendiceal luminal obstruction → distension → ischaemia → bacterial infection ^[1]
• Why it is listed: Both cause acute abdominal pain with fever and leukocytosis. However, appendicitis typically presents with periumbilical pain migrating to RIF (McBurney's point), not RUQ. Jaundice is absent. Listed as a DDx primarily because of the overlap in the "acute abdomen with fever and leucocytosis" category.

10. Primary Sclerosing Cholangitis (PSC)

• Mechanism: Chronic progressive inflammation, fibrosis, and stricturing of both intra- and extrahepatic bile ducts of unknown aetiology ^[14]
• Why it mimics Mirizzi: Both can cause obstructive jaundice at the hilar level ^[3]. Both can cause cholangitis.
• How to distinguish: PSC has a strong association with ulcerative colitis ^[14]. Cholangiogram (MRCP/ERCP) shows "beaded" pattern of multifocal strictures alternating with dilatation throughout the biliary tree — very different from the focal hilar obstruction of Mirizzi. p-ANCA positive in ~80%. No gallstone at GB neck.

11. Biliary Leaks

• Mechanism: Post-surgical or post-traumatic disruption of bile duct integrity
• Why it mimics Mirizzi: Both can cause jaundice and biliary collections. However, biliary leaks present in the post-operative context. HIDA scan or ERCP demonstrates active extravasation of bile.

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DDx Approach: Differentiating Stone vs. Tumour

In the history, differentiate stone vs tumour ^[4]:

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Mermaid Diagram: DDx Algorithm for Suspected Mirizzi Syndrome

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Summary Table: Complete DDx at a Glance

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Active Recall - Mirizzi Syndrome Differential Diagnosis

1. Mirizzi syndrome is classified as what type of biliary obstruction (intraluminal, mural, or extramural)? Why?

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Extramural. The stone is in the cystic duct/Hartmann's pouch (outside the bile duct), compressing the CHD from the outside. The stone is not within the CBD lumen (intraluminal) nor is the pathology in the bile duct wall itself (mural).

2. What is the single most helpful USG finding that distinguishes Mirizzi syndrome from choledocholithiasis?

Your answer

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In Mirizzi: dilated intrahepatic ducts above the GB neck level + stone impacted at GB neck + normal-calibre CBD below. In choledocholithiasis: the CBD itself is dilated with a stone visible within the CBD lumen.

3. A patient with known gallstones presents with acute cholecystitis but has disproportionately significant jaundice and dilated intrahepatic ducts on USG. What diagnosis should you suspect and why?

Your answer

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Mirizzi syndrome. In uncomplicated acute cholecystitis, jaundice is usually absent or mild because obstruction is limited to gallbladder outflow (cystic duct) without CHD compression. Significant jaundice with intrahepatic duct dilatation indicates CHD obstruction, which in the setting of a stone at GB neck suggests Mirizzi syndrome.

4. Name 3 conditions that are exceptions to Courvoisier's Law (jaundice + palpable GB from stone-related causes).

Your answer

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1. Mirizzi syndrome (stone at GB neck compresses CHD while GB body distends). 2. Double impaction (stone in cystic duct causing GB distension + stone in distal CBD causing jaundice). 3. Recurrent pyogenic cholangitis (pathology is in bile ducts, not GB, so GB is not fibrosed and can distend).

5. Why must CT abdomen with contrast be performed in all suspected Mirizzi syndrome cases?

Your answer

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To rule out concurrent gallbladder carcinoma (5-28% coexistence rate) and other malignancies. CT can demonstrate enhancing mass lesions, porta hepatis lymphadenopathy, and hepatic infiltration/metastasis that would indicate malignancy rather than (or in addition to) Mirizzi syndrome.

6. How does RPC differ from Mirizzi syndrome in terms of stone type, stone location, and imaging pattern?

Your answer

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RPC: brown pigment/calcium bilirubinate stones, formed de novo in intrahepatic ducts, imaging shows intrahepatic duct dilatation with strictures (left lobe predominance) and intrahepatic stones. Mirizzi: usually cholesterol stones formed in gallbladder, impacted at Hartmann's pouch/cystic duct, imaging shows dilated ducts above GB neck with normal CBD below and no intrahepatic stones.

References

^[1] Senior notes: felixlai.md (Mirizzi syndrome DDx and diagnosis, pp. 572–574; Cholecystitis and Mirizzi, p. 556) ^[2] Senior notes: maxim.md (Mirizzi syndrome, pp. 130–132; Courvoisier's Law and exceptions, p. 130) ^[3] Senior notes: felixlai.md (Causes of obstructive jaundice by level of obstruction, p. 500) ^[4] Senior notes: maxim.md (Obstructive jaundice DDx and approach, p. 251) ^[5] Senior notes: maxim.md (Choledocholithiasis, p. 136) ^[6] Senior notes: maxim.md (Acute calculous cholecystitis, p. 131) ^[7] Senior notes: felixlai.md (Cholecystitis overview, p. 553) ^[8] Senior notes: felixlai.md (Acute cholecystitis physical examination — jaundice and Mirizzi, p. 556) ^[9] Senior notes: maxim.md (Gallbladder carcinoma, pp. 138–139) ^[10] Senior notes: maxim.md (Cholangiocarcinoma classification and risk factors, pp. 139–140) ^[11] Senior notes: felixlai.md (Recurrent pyogenic cholangitis, pp. 526–527); Senior notes: maxim.md (RPC, p. 136) ^[12] Senior notes: maxim.md (Choledochal cyst, p. 138) ^[13] Senior notes: felixlai.md (Acute pancreatitis, pp. 579–580) ^[14] Senior notes: felixlai.md (Primary sclerosing cholangitis, p. 529)

Diagnostic Criteria for Mirizzi Syndrome

Why There Are No Formal "Diagnostic Criteria"

Unlike acute cholecystitis (Tokyo Guidelines 2018) or acute cholangitis (Tokyo Guidelines 2018), there is no universally accepted set of formal diagnostic criteria for Mirizzi syndrome. The diagnosis is made by combining clinical suspicion with imaging findings. In fact, the majority of cases are diagnosed intraoperatively — only about 8–27% of cases are diagnosed preoperatively ^[1][2].

This is because:

1. The clinical presentation is non-specific — it overlaps with cholecystitis, choledocholithiasis, and cholangitis
2. The pathognomonic finding (stone at GB neck compressing CHD ± cholecystobiliary fistula) requires high-quality imaging to detect
3. The dense pericholecystic inflammation makes anatomical delineation difficult even on cross-sectional imaging

Working Diagnostic Framework

While no formal criteria exist, the diagnosis rests on demonstrating the following:

When the patient also presents with features of acute cholangitis, the Tokyo Guidelines 2018 (TG18) criteria for cholangitis apply in parallel ^[7]:

Suspected cholangitis: ONE systemic inflammation criterion (fever/rigors OR abnormal WBC/CRP) AND ONE cholestasis criterion (jaundice OR abnormal LFTs)

Definite cholangitis: Suspected criteria met PLUS biliary dilatation on imaging AND evidence of aetiology (stone, stricture, stent) on imaging ^[7]

When the patient presents with features of acute cholecystitis, the Tokyo Guidelines 2018 (TG18) criteria for cholecystitis apply ^[8]:

• A: Local signs (Murphy's sign, RUQ mass/pain/tenderness)
• B: Systemic signs (fever, leukocytosis, elevated CRP)
• C: Imaging findings characteristic of acute cholecystitis
• Suspected = A + B; Definite = A + B + C ^[8]

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Diagnostic Algorithm

The diagnostic workup for suspected Mirizzi syndrome follows a logical stepwise approach: Bloods → USG → CT → MRCP → ERCP. Each modality answers a specific question:

Mermaid Diagnostic Algorithm

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Investigation Modalities: Detailed Findings and Interpretation

1. Blood Tests (Laboratory Investigations)

Blood tests do not diagnose Mirizzi syndrome per se, but they characterise the degree of obstruction, infection, and fitness for intervention.

a. Complete Blood Count with Differentials (CBC D/C)

• Expected finding: Leukocytosis ^[1]
• Why: Leukocytosis (↑ WBC with neutrophil predominance and left shift / band forms) indicates an acute inflammatory/infectious process — present in concurrent acute cholecystitis, cholangitis, or pancreatitis ^[1]
• Interpretation:
  • Mild leukocytosis (12,000–15,000/µL) → uncomplicated cholecystitis
  • Marked leukocytosis ( > 20,000/µL) → suggests complicated disease (empyema, gangrenous cholecystitis, or suppurative cholangitis) ^[8]
• Also check: Thrombocytopenia — relevant when planning invasive procedures such as ERCP (need adequate platelets for sphincterotomy) ^[3][15]
• In patients with underlying cirrhosis: pancytopenia from hypersplenism may be present ^[15]

b. Liver Function Tests (LFT)

• Expected finding: ↑ ALP and bilirubin ^[1] — the classic cholestatic pattern
• Why: CHD obstruction prevents bile from draining into the duodenum
  • ↑ Conjugated bilirubin: bile cannot flow → backs up into blood → conjugated (water-soluble) bilirubin spills into circulation
  • ↑ ALP (alkaline phosphatase): ALP is concentrated in bile duct epithelium. Obstruction → back-pressure → induction of ALP synthesis + leakage into blood. The biliary isoenzyme is predominant.
  • ↑ GGT (gamma-glutamyl transferase): rises in parallel with ALP in cholestasis; confirms biliary origin of ALP elevation ^[3][15]
  • Transaminases (AST/ALT): may be mildly elevated (back-pressure hepatocyte injury) but typically NOT dramatically elevated unless acute biliary obstruction with "transaminitis" from sudden complete obstruction

c. Clotting Profile (PT/INR)

• Expected finding: Prolonged PT/INR in prolonged obstruction ^[3][15]
• Why: Obstructive jaundice → no bile salts reaching the gut → impaired absorption of fat-soluble vitamin K → vitamin K is a cofactor for hepatic γ-carboxylation of clotting factors II, VII, IX, X → coagulopathy ^[3]
• Clinical importance: Must be corrected before any invasive procedure. Give Vitamin K 10 mg IV/IM at least 24–48 hours before surgery or ERCP. If urgent, give Fresh Frozen Plasma (FFP) for immediate correction ^[3]
• Diagnostic value: If PT corrects with vitamin K → the liver is still functional (just vitamin K deficient). If PT does NOT correct → hepatocellular dysfunction (liver cannot synthesise factors regardless of vitamin K availability)

d. Inflammatory Markers

• CRP: Elevated in acute inflammation/infection (cholecystitis, cholangitis)
• ESR: Less specific, may be elevated ^[7]

e. Renal Function Tests (RFT)

• Why: Obstructive jaundice predisposes to hepatorenal syndrome and renal impairment (cholestasis → endotoxin-mediated renal vasoconstriction). Also essential as baseline before any contrast-enhanced imaging or ERCP ^[7]

f. Serum Amylase / Lipase

• Why: To rule out concurrent acute pancreatitis ^[1]. A stone in Hartmann's pouch can occasionally also cause pancreatitis if there is distal migration or ampullary impaction. Amylase > 3× upper limit of normal suggests pancreatitis.

g. Blood and Bile Cultures

• Why: If cholangitis is suspected, blood cultures MUST be sent before starting antibiotics ^[16]. Common organisms: Gram-negatives (E. coli, Klebsiella), enterococci. Positive bile cultures are common with biliary obstruction ^[7].

h. Tumour Markers

• CEA and CA 19-9: May be checked to evaluate for concurrent malignancy (gallbladder carcinoma or cholangiocarcinoma), but are NOT diagnostically useful since they lack sensitivity and specificity ^[15]. Their role is primarily in serial monitoring after resection for recurrence detection, not in primary diagnosis.

Summary of expected blood findings in Mirizzi syndrome: Leukocytosis, ↑ ALP, ↑ GGT, ↑ conjugated bilirubin, ± prolonged PT, ± elevated amylase (if concurrent pancreatitis), ± positive blood cultures (if cholangitis).

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2. USG Abdomen (First-Line Imaging)

Why USG first? It is readily available, non-invasive, does not involve radiation or contrast, and is the standard first-line investigation for any patient with RUQ pain or obstructive jaundice ^[1][2][4].

Key Findings Suggestive of Mirizzi Syndrome [1][2]

Limitations of USG

• Operator-dependent: requires experienced sonographer ^[6]
• Limited by body habitus: obesity and bowel gas reduce image quality
• Cannot reliably demonstrate the cholecystobiliary fistula — this usually requires ERCP or MRCP
• Cannot exclude malignancy — a contracted, inflamed GB with pericholecystic changes can look similar to GB carcinoma on USG
• Distal CBD poorly visualized: overlying duodenal gas obscures this region ^[4][5]

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3. CT Abdomen with Contrast

Why CT? The primary role of CT is to determine whether malignancy is present ^[1][2].

Key Findings and Their Interpretation

Why CT Cannot Definitively Diagnose Mirizzi

CT is not very sensitive for biliary stones (only ~75% of gallstones are visible on CT ^[4]) and cannot reliably demonstrate a cholecystobiliary fistula. Its main value is excluding malignancy and evaluating the extent of inflammation.

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4. MRCP (Magnetic Resonance Cholangiopancreatography)

MRCP = "MR" (magnetic resonance) + "CP" (cholangiopancreatography) — non-invasive imaging of the biliary tree and pancreatic duct using heavily T2-weighted sequences where fluid (bile) appears bright white ^[4].

Why MRCP? It has high sensitivity for Mirizzi syndrome ^[1] and plays a critical role in:

1. Delineating biliary anatomy preoperatively
2. Differentiating inflammatory from neoplastic pathology
3. Avoiding the complications of ERCP in diagnostic-only scenarios

Key Findings and Their Interpretation

Advantages of MRCP over Other Modalities

• Non-contrast, non-invasive ^[4] — no iodinated contrast, no radiation
• Superior to USG in detecting stones in the cystic duct ^[8]
• Excellent for visualising the entire biliary tree in one image
• Can identify concurrent choledocholithiasis (stones within CBD)
• Differentiates inflammatory vs neoplastic mass — the key advantage over USG and CT ^[1]

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5. ERCP (Endoscopic Retrograde Cholangiopancreatography)

ERCP = "E" (endoscopic) + "R" (retrograde) + "C" (cholangio-) + "P" (pancreatography) — an endoscopic procedure where a side-viewing duodenoscope is used to cannulate the ampulla of Vater and inject contrast retrogradely into the biliary and pancreatic ducts under fluoroscopy.

Why ERCP? Both diagnostic and therapeutic ^[1][2] — this is the gold standard for:

1. Confirming Mirizzi syndrome
2. Determining if cholecystobiliary fistula is present (critical for Csendes classification) ^[1][2]
3. Biliary decompression (stenting) as a bridge to definitive surgery

Key Findings on Cholangiography [1]

Therapeutic Interventions Performed at ERCP [1][2]

Complications of ERCP

ERCP is invasive and carries significant risks:

• Post-ERCP pancreatitis (most common, ~3–5%) — guidewire or contrast traumatises the pancreatic duct orifice
• Perforation (duodenal or bile duct)
• Haemorrhage (from sphincterotomy site)
• Cholangitis (introducing bacteria with instrumentation)
• Bacteraemia — hence antibiotic prophylaxis is required ^[4]

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6. Additional / Adjunct Investigations

a. Intraoperative Cholangiogram (IOC)

• Performed during cholecystectomy by injecting contrast via the cystic duct under fluoroscopy
• Many cases of Mirizzi syndrome are first diagnosed intraoperatively via IOC when the surgeon encounters unexpected biliary anatomy or a fistula
• Exploration of CBD (ECBD) should be performed in all patients with cholecystobiliary fistula to rule out concomitant choledocholithiasis unless already done endoscopically ^[1]

b. Percutaneous Transhepatic Cholangiography (PTC / PTBD)

• Preferred to ERCP when obstruction is at or above the level of the hepatic confluence ^[4]
• In Mirizzi syndrome (hilar-level obstruction), PTC can access the dilated intrahepatic system from above and provide drainage
• Complications: bacteraemia, haemobilia ^[4]
• Rarely needed as ERCP can usually manage Mirizzi syndrome adequately

c. Endoscopic Ultrasound (EUS)

• Can provide detailed images of the GB neck, cystic duct, and adjacent structures
• Useful for FNAC or trucut biopsy if there is suspicion of malignancy ^[15]
• Less commonly used in Mirizzi workup specifically but valuable when imaging is equivocal for malignancy

d. HIDA Scan (Hepatobiliary Iminodiacetic Acid Scan / Cholescintigraphy)

• Primarily used for acute cholecystitis (non-visualisation of GB = cystic duct obstruction) ^[4][8]
• Not specific for Mirizzi syndrome but may show non-filling of the gallbladder (cystic duct obstruction) + delayed hepatic clearance (CHD obstruction)
• Largely replaced by MRCP in Mirizzi workup

e. AXR (Plain Abdominal X-ray)

• Limited utility in Mirizzi specifically
• Only ~15% of gallstones are radio-opaque ^[6]
• However, if there is concurrent gallstone ileus (Csendes Type 5B): look for Rigler's triad: pneumobilia + small bowel obstruction + ectopic gallstone ^[2]

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Summary: Investigations at a Glance

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Active Recall - Mirizzi Syndrome Diagnosis and Investigations

1. What is the characteristic USG triad suggestive of Mirizzi syndrome?

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(1) Stone impacted in the gallbladder neck/Hartmann's pouch. (2) Dilatation of biliary system above the level of gallbladder neck (intrahepatic duct dilatation). (3) Abrupt change to normal width of CBD below the level of stones. Also: contracted gallbladder with gallstones.

2. What are the pathognomonic ERCP findings in Mirizzi syndrome? Describe how you would identify a cholecystobiliary fistula on ERCP.

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ERCP findings: (1) Stone in neck of GB or cystic duct. (2) Eccentric or excavating defect on the lateral wall of CBD at the level of cystic duct / GB neck (not a central filling defect). (3) Cholecystobiliary fistula is demonstrated by passage of contrast from proximal dilated biliary channels into the gallbladder (contrast should not enter GB if cystic duct is obstructed by stone - if it does, there is a fistulous communication).

3. Why is MRCP considered superior to USG and CT in differentiating Mirizzi syndrome from gallbladder carcinoma?

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T2-weighted MRCP images can differentiate between a neoplastic mass and an inflammatory mass based on signal characteristics (inflammatory tissue shows T2 hyperintensity due to oedema/high water content; neoplastic tissue shows heterogeneous/lower T2 signal). This differentiation may not be possible on abdominal USG or CT scan. MRCP also shows extent of pericholecystic inflammation and precise biliary anatomy.

4. List 3 therapeutic interventions that can be performed at ERCP in a patient with Mirizzi syndrome.

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(1) Sphincterotomy (cutting sphincter of Oddi to facilitate stent/stone passage). (2) Biliary stenting with endoprosthesis placement for temporary decompression of the biliary tree. (3) Stone extraction (if concomitant CBD stones found) using wire baskets, extraction balloons, or mechanical lithotripsy.

5. A patient with obstructive jaundice from suspected Mirizzi syndrome has a prolonged PT/INR. Explain the mechanism and how you would correct it before ERCP.

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Mechanism: Obstructive jaundice prevents bile salts from reaching the gut, impairing absorption of fat-soluble vitamin K. Vitamin K is required as a cofactor for hepatic gamma-carboxylation of clotting factors II, VII, IX, and X. Deficiency leads to prolonged PT/INR. Correction: Give vitamin K 10 mg IV/IM at least 24-48 hours before ERCP. If urgent, give FFP for immediate correction. If PT corrects with vitamin K, liver synthetic function is intact (pure malabsorption). If it does not correct, suspect hepatocellular dysfunction.

6. Why should CT abdomen with contrast be performed in all patients with suspected Mirizzi syndrome, even if USG already suggests the diagnosis?

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CT is essential to rule out concurrent malignancy, specifically gallbladder carcinoma (5-28% coexistence rate). CT can demonstrate enlarged porta hepatis lymph nodes, hepatic infiltration or metastasis, and enhancing mass lesions that would indicate malignancy. USG cannot reliably exclude malignancy due to the dense pericholecystic inflammation that mimics a neoplastic mass.

References

^[1] Senior notes: felixlai.md (Mirizzi syndrome diagnosis, pp. 573–574; treatment and ECBD, p. 575) ^[2] Senior notes: maxim.md (Mirizzi syndrome investigations and management, pp. 131–132) ^[3] Lecture slides: Malignant biliary obstruction.pdf (Manifestations of pathophysiological disturbance of MBO: bleeding tendency, infection, poor wound healing) ^[4] Senior notes: maxim.md (HBP investigations: USG, MRCP, ERCP, PTC, pp. 250–251) ^[5] Senior notes: maxim.md (Choledocholithiasis investigations and stone removal, p. 136) ^[6] Senior notes: maxim.md (Biliary colic investigations: USG, AXR, p. 130) ^[7] Senior notes: felixlai.md (Acute cholangitis diagnostic criteria — Tokyo Guidelines, p. 521) ^[8] Senior notes: felixlai.md (Acute cholecystitis diagnostic criteria — Tokyo Guidelines 2013, physical examination, pp. 555–557) ^[15] Senior notes: felixlai.md (MBO biochemical tests and radiological tests, pp. 502–503) ^[16] Senior notes: maxim.md (Acute cholangitis urgent investigations — blood culture, p. 135)

Management of Mirizzi Syndrome

Overarching Principles

Before diving into type-specific surgery, let's establish the fundamental management philosophy. There are three layers to managing Mirizzi syndrome:

1. Acute stabilisation — resuscitate, treat sepsis, decompress the biliary tree
2. Preoperative optimisation — correct coagulopathy, reduce bilirubin, ensure fitness for surgery
3. Definitive surgery — remove the gallbladder and impacted stone, and address any cholecystobiliary fistula according to Csendes type

Surgery is the mainstay of therapy permitting removal of causal factors including the inflamed gallbladder and the impacted stones ^[1].

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Phase 1: Acute Stabilisation and Resuscitation

If the patient presents with acute cholangitis (Charcot's triad or Reynolds' pentad) or acute cholecystitis, immediate management follows the RAD principle ^[16]:

R — Resuscitation

• NPO (nil per os) — bowel rest
• IV fluid resuscitation — correct dehydration and maintain urine output
• Monitor vitals and I/O — look for signs of shock (hypotension, tachycardia, oliguria, altered mental status, cold clammy skin) ^[7]
• Continuous monitoring of vitals to look for signs of failure of conservative treatment: ↑ Temperature / Pulse; ↓ BP / Consciousness level / Urine output; Increased abdominal tenderness and guarding ^[7]

A — Antibiotics

• IV broad-spectrum antibiotics targeting Gram-negative rods and anaerobes ^[17][18]:
  • Mild: IV Augmentin (amoxicillin-clavulanate) ^[16]
  • Severe: IV Tazocin (piperacillin-tazobactam) ^[16]
  • Alternatives: Cefuroxime + Metronidazole ^[17][18]
  • Duration: typically 7 days, adjusted based on culture results

Why these antibiotics? The common biliary pathogens are enteric Gram-negatives (E. coli, Klebsiella) and anaerobes. Augmentin covers these adequately for mild cases. Tazocin has broader Gram-negative and Pseudomonas coverage for severe/nosocomial infections. Metronidazole specifically covers anaerobes.

D — Drainage (Biliary Decompression)

• 15% of patients will NOT respond to antibiotics alone and require emergency biliary decompression ^[7]
• Indications for urgent drainage:
  • Reynolds' pentad (suppurative cholangitis with shock) ^[16]
  • Not responding to antibiotics for 24 hours ^[16] — because obstruction impairs secretion of antibiotics into bile, antibiotics alone cannot sterilise an obstructed system
  • Progressive clinical deterioration despite maximal medical therapy

Hierarchy of drainage (QMH practice: ERCP → PTBD → ECBD) ^[7]:

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Phase 2: Preoperative Optimisation

Once the acute episode is controlled, the patient must be optimised before definitive surgery:

Definitive treatment should be deferred until cholangitis has been treated and the proper diagnosis is established ^[7]

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Phase 3: Definitive Surgical Management — By Csendes Type

The treatment approach is based on the presence and type of cholecystobiliary fistula ^[1][2].

This is the core exam-testable content. The logic is straightforward:

• No fistula (Type I): Remove the gallbladder — the bile duct wall is intact, no repair needed
• Small fistula (Type II): Remove the gallbladder + close the small hole in the bile duct
• Moderate fistula (Type III): The hole is too big for simple closure — consider bilioenteric anastomosis
• Complete destruction (Type IV): The entire CBD wall is gone — you MUST bypass with bilioenteric anastomosis
• Cholecystoenteric fistula (Type V): Address the bowel problem (gallstone ileus if present) AND the biliary fistula

Type I: No Cholecystobiliary Fistula

Pathology: Extrinsic compression of CHD by stone — bile duct wall intact.

Surgery: Partial or total cholecystectomy (laparoscopic or open) ^[1]

• ECBD (exploration of CBD) is typically NOT required ^[1] — because there is no fistula and the bile duct wall is intact, there is nothing to repair in the CBD
• Laparoscopic approach is feasible in select cases but carries high risk of conversion to open due to dense adhesions
• If the critical view of safety cannot be achieved (anatomy distorted by inflammation), consider:
  • Intraoperative cholangiogram (IOC) to delineate anatomy
  • Subtotal (partial) cholecystectomy — leave the posterior wall of the GB attached to the liver bed and remove the rest, rather than risking bile duct injury by forcing a complete dissection

Why laparoscopic is difficult: Laparoscopic management of Mirizzi syndrome can be difficult due to dense adhesions and edematous inflammatory tissue cause distortion of normal anatomy and increase the risk of biliary injury ^[1]. Calot's triangle is obliterated by fibrosis. The cystic duct, cystic artery, and CHD are fused together. The Critical View of Safety — normally requiring clear identification of only two structures entering the gallbladder (cystic duct and cystic artery) with clearance of the hepatocystic triangle and cystic plate ^[20][21] — is often impossible to obtain.

Type II: Fistula < 1/3 CBD Circumference

Pathology: Small cholecystobiliary fistula — most of the CBD wall is intact.

Surgery: Cholecystectomy plus closure of fistula ^[1] using one of:

• Suture repair with absorbable material — primary closure of the small defect in the bile duct wall
• T-tube placement — a T-shaped tube placed in the CBD to stent the repair, with the long limb exiting through the abdominal wall. Allows postoperative cholangiogram to check for leaks and residual stones. The T-tube is removed after 2–4 weeks once a fibrous tract has formed.
• Choledochoplasty with remnant gallbladder — using a pedicled flap of the gallbladder wall (the remnant after subtotal cholecystectomy) to patch the defect in the CBD. This is elegant because it uses autologous tissue with a blood supply.

Why these options? The defect is small ( < 1/3 circumference), so the remaining CBD wall has enough structural integrity to support a primary repair. There is no need for a bypass because the duct can be reconstructed.

Type III: Fistula 1/3–2/3 CBD Circumference

Pathology: Moderate-sized fistula — significant CBD wall destruction but not complete.

Surgery: Cholecystectomy OR bilioenteric anastomosis ^[1]

• Bilioenteric anastomosis includes choledochoduodenostomy, choledochojejunostomy, or cholecystoduodenostomy ^[1]
• Suture of the fistula is NOT required ^[1] — because the defect is too large for primary closure; attempting to close it would cause stricture due to tension on the suture line

Why bilioenteric anastomosis? When > 1/3 of the CBD circumference is destroyed, primary repair would narrow the duct lumen (tension on the remaining edges), leading to postoperative biliary stricture. Instead, you bypass the damaged segment by connecting the proximal healthy bile duct directly to a loop of bowel, allowing bile to drain into the intestine via a new route.

The choice between different anastomosis types:

• Choledochoduodenostomy: simpler; CBD → duodenum. Risk of "sump syndrome" (food debris/bacteria accumulating in the CBD stump distal to the anastomosis)
• Choledochojejunostomy (Roux-en-Y): CBD → jejunal limb. More complex but lower risk of reflux cholangitis because the Roux limb keeps food/bacteria away from the biliary anastomosis
• Cholecystoduodenostomy is rarely used

Type IV: Fistula > 2/3 CBD Circumference (Complete Destruction)

Pathology: Near-complete or complete destruction of the CBD wall.

Surgery: Bilioenteric anastomosis — typically choledochojejunostomy since the entire wall of CBD has been destroyed ^[1]

Why choledochojejunostomy specifically? With complete CBD wall destruction, there is no CBD left to repair. You must create a Roux-en-Y hepaticojejunostomy/choledochojejunostomy — bringing a loop of jejunum up to the proximal healthy bile duct (common hepatic duct or hepatic duct stumps) and creating an end-to-side or side-to-side anastomosis. The Roux-en-Y configuration is preferred over choledochoduodenostomy in this scenario because it provides a longer defunctioned limb, reducing the risk of ascending cholangitis from intestinal content reflux.

Type V: Any Type + Cholecystoenteric Fistula ± Gallstone Ileus

Pathology: Mirizzi syndrome (any Csendes type) coexisting with a cholecystoenteric fistula (communication between GB and bowel) ^[2]. If a large stone has passed into the bowel and caused obstruction → gallstone ileus (Type 5B).

Surgery — Two separate problems to address:

A. If gallstone ileus present (Type 5B) — address the bowel obstruction first:

• Enterolithotomy to relieve SBO ^[2]:
  • Exploratory laparotomy
  • Proximal enterotomy (NOT over the stone because of ulceration) ^[2] — the bowel wall at the site of stone impaction is inflamed and ulcerated; cutting there risks breakdown of the enterotomy closure
  • Milk the stone proximally for extraction ^[2]
  • Inspect the entire bowel for additional stones (second stone found in ~3–16% of cases)
• Then: Same-session or elective cholecystectomy + fistula repair ^[2]

B. Biliary fistula — manage per the corresponding Csendes type (I–IV) as described above

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Summary Table: Type-Specific Surgical Management

ECBD should be performed in all patients with cholecystobiliary fistula to rule out concomitant choledocholithiasis (CBD stones) unless it has been performed endoscopically ^[1]

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Open vs Laparoscopic Approach

With fistula (Types II–V): open surgery ^[2]:

• GB: Subtotal cholecystectomy (severe inflammation impedes safe dissection of Calot's triangle) ^[2]
• CBD: Closure of fistula / choledochoplasty / bilioenteric anastomosis (choledochojejunostomy) depending on size of defect ^[2]

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Special Situations

Concurrent Gallbladder Carcinoma

If intraoperative frozen section reveals gallbladder carcinoma:

• Abort the standard Mirizzi surgery
• Proceed to oncological resection: open cholecystectomy with intraoperative frozen section → if beyond stage T1a, perform extended cholecystectomy with en-bloc resection of liver segments IVb/V, extrahepatic bile duct resection (if cystic duct margin involved), and regional lymphadenectomy ^[9]

Patient Unfit for Surgery

• Percutaneous cholecystostomy: drainage of the gallbladder for patients who are haemodynamically unstable, high surgical risk, or have severe comorbidities ^[22][18]
  • Indications: high surgical risk, haemodynamically unstable, difficult cholecystectomy ^[18]
  • Can be percutaneous (USG/CT-guided) or endoscopic (ERCP/EUS-guided)
  • Allows decompression and infection control as a bridge to interval surgery or as definitive palliation in the very frail
• Long-term ERCP stenting can be used as definitive palliation in patients truly unfit for any surgery — stent exchanges every 3–6 months to prevent occlusion

Non-Operative Management with ERCP Alone

In very select cases (elderly, high ASA grade, Type I only), some centres have reported managing Mirizzi Type I non-operatively with ERCP stone extraction ± electrohydraulic lithotripsy, but this is not standard of care and recurrence is high.

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Management Algorithm — Mermaid Diagram

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Contraindications and Cautions

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Postoperative Considerations

• T-tube management (if placed):

  • Check tube cholangiogram at 7–10 days postoperatively to confirm no leak and no residual stones
  • If cholangiogram is normal → clamp T-tube → if patient tolerates (no pain, no fever) → remove after fibrous tract has matured (~2–4 weeks)
  • T-tubes have been shown to increase complications (infection, bile leak, tube dislodgement) compared to primary closure ^[5]

• Follow-up imaging: USG at 3–6 months to assess for biliary stricture (a late complication of fistula repair)

• Histopathology: Send all gallbladder specimens for histological examination — given the 5–28% risk of concurrent gallbladder carcinoma, intraoperative frozen section and final histology are essential

• Long-term: Monitor for biliary stricture, recurrent cholangitis, or missed malignancy

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Active Recall - Mirizzi Syndrome Management

1. What is the definitive treatment for Mirizzi syndrome? Why can ERCP alone not be the definitive treatment?

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Definitive treatment is surgery (cholecystectomy + management of fistula based on Csendes type). ERCP alone is not definitive because the causative stone is impacted in the GB neck/Hartmann's pouch, not in the CBD — it cannot be extracted endoscopically from the CBD. ERCP provides only temporary biliary decompression via stenting as a bridge to surgery.

2. Describe the surgical management for Csendes Type II vs Type IV Mirizzi syndrome and explain the rationale for the difference.

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Type II (fistula < 1/3 CBD): Cholecystectomy + closure of fistula by suture repair with absorbable material, T-tube placement, or choledochoplasty with GB remnant. Rationale: the defect is small and the remaining CBD wall has structural integrity for primary repair. Type IV (fistula > 2/3 CBD, complete destruction): Bilioenteric anastomosis, typically Roux-en-Y choledochojejunostomy. Rationale: the entire CBD wall is destroyed so there is nothing to repair; must bypass the damaged segment by connecting proximal bile duct directly to jejunum.

3. In Mirizzi syndrome Types II-V, why is open surgery preferred over laparoscopic? What surgical technique is used for the gallbladder?

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Open surgery preferred because: (1) fistula requires complex biliary reconstruction not easily done laparoscopically, (2) dense adhesions and edematous tissue distort anatomy and increase risk of biliary injury. Subtotal cholecystectomy is used because severe inflammation impedes safe dissection of Calot's triangle — leaving the posterior GB wall on the liver bed avoids injury to the bile duct and hepatic artery.

4. What is the hierarchy of biliary drainage in acute cholangitis complicating Mirizzi syndrome at QMH? When is surgical drainage indicated?

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Hierarchy: ERCP (1st line) then PTBD (2nd line) then ECBD (3rd line). Surgical drainage (ECBD with T-tube) is indicated when: (1) failure of endoscopic drainage, or (2) deterioration despite endoscopic drainage. ECBD carries high mortality (~30%) and is reserved as last resort.

5. Why must ECBD be performed in all patients with cholecystobiliary fistula (Csendes Types II-IV)?

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To rule out concomitant choledocholithiasis (CBD stones). Once a cholecystobiliary fistula exists, stones can migrate from the gallbladder through the fistula into the CBD. Missing residual CBD stones would lead to recurrent cholangitis and obstruction postoperatively. ECBD is not required if stone clearance has already been confirmed endoscopically by ERCP.

6. A patient with Mirizzi syndrome Type V-B presents with small bowel obstruction. Describe the surgical management of the bowel obstruction, including the specific technique and its rationale.

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Enterolithotomy to relieve SBO: exploratory laparotomy, proximal enterotomy (NOT over the stone because bowel wall at impaction site is ulcerated and prone to breakdown), milk the stone proximally for extraction. Inspect entire bowel for additional stones (3-16% have second stone). Then same-session or elective cholecystectomy + cholecystoenteric fistula repair + manage biliary fistula per Csendes type.

References

^[1] Senior notes: felixlai.md (Mirizzi syndrome treatment, pp. 574–575) ^[2] Senior notes: maxim.md (Mirizzi syndrome management and gallstone ileus, pp. 131–132) ^[3] Lecture slides: Malignant biliary obstruction.pdf (Manifestations of pathophysiological disturbance of MBO) ^[5] Senior notes: maxim.md (Choledocholithiasis management — T-tube complications, p. 136) ^[7] Senior notes: felixlai.md (Acute cholangitis treatment — biliary decompression hierarchy, QMH practice, p. 522) ^[9] Senior notes: maxim.md (Gallbladder carcinoma treatment — extended cholecystectomy, p. 139) ^[16] Senior notes: maxim.md (Acute cholangitis acute management — RAD, p. 135) ^[17] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (Acute cholangitis management — ERCP, antibiotics, ECBD, pp. 13–15) ^[18] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (Cholecystostomy indications, p. 12) ^[19] Senior notes: felixlai.md (ERCP is always 1st line for biliary drainage, p. 504) ^[20] Senior notes: felixlai.md (Cholecystectomy — CVS, conversion to open, subtotal cholecystectomy, pp. 513–514) ^[21] Senior notes: maxim.md (Critical View of Safety, p. 133) ^[23] Senior notes: felixlai.md (ERCP contraindications, p. 87)

Complications of Mirizzi Syndrome

Complications of Mirizzi syndrome can be organised into three categories:

1. Complications of the disease itself (from the pathological process of stone impaction, CHD compression, and chronic inflammation)
2. Complications of associated conditions (from concurrent cholecystitis, cholangitis, pancreatitis)
3. Complications of treatment (from ERCP and from surgery)

Understanding why each complication occurs — tracing it back to the underlying pathophysiology — is far more useful than memorising a list.

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A. Complications of the Disease Process

These arise directly from the stone impaction, chronic inflammation, and biliary obstruction that define Mirizzi syndrome.

1. Cholecystobiliary Fistula (Csendes Types II–IV)

• Mechanism: The impacted stone exerts chronic pressure on the adjacent bile duct wall. Combined with inflammation-mediated ischaemia and pressure necrosis, the stone erodes through the gallbladder/cystic duct wall and the CHD/CBD wall, creating an abnormal communication ^[1][2]
• Why it matters: This is not just a complication — it defines the progression of Mirizzi syndrome from Type I (compression only) to Types II–IV. The fistula fundamentally changes the surgical approach: primary repair vs. bilioenteric anastomosis. The larger the fistula, the more complex the surgery.
• Consequence: Once a fistula exists, stones can migrate from the gallbladder into the CBD (causing secondary choledocholithiasis), and the structural integrity of the bile duct is compromised

2. Gallbladder Carcinoma (CA Gallbladder)

• Mechanism: Recurrent inflammation and biliary stasis may predispose to both conditions ^[1]. The chronic inflammatory milieu — repeated cycles of mucosal injury, regeneration, and fibrosis — drives a dysplasia-carcinoma sequence (analogous to Barrett's → oesophageal adenocarcinoma, or UC → colorectal cancer). Chronic inflammation generates reactive oxygen species, DNA damage, and promotes proliferative signalling.
• CA gallbladder is a recognized complication/association of Mirizzi syndrome ^[2]. Reported coexistence rate: 5–28% across various surgical series.
• Why it matters: This is the reason you must always perform CT abdomen + contrast preoperatively (to look for enlarged porta hepatis LNs or hepatic infiltration of metastasis ^[1]) and why MRCP is important (T2-weighted images can differentiate between a neoplastic and inflammatory mass ^[1]). Intraoperative frozen section of the gallbladder specimen should always be sent.

3. Choledocholithiasis (Secondary CBD Stones)

• Mechanism: Once a cholecystobiliary fistula forms (Types II–IV), gallstones can migrate from the gallbladder through the fistula directly into the CBD. Additionally, bile stasis proximal to the obstruction promotes de novo stone formation within the bile ducts.
• Why it matters: This is why ECBD should be performed in all patients with cholecystobiliary fistula to rule out concomitant choledocholithiasis (CBD stones) unless it has been performed endoscopically ^[1]. Missed CBD stones after Mirizzi surgery will cause recurrent cholangitis and obstructive jaundice.

4. Cholecystoenteric Fistula and Gallstone Ileus (Csendes Type V)

• Mechanism: The same chronic inflammatory and erosive process that creates a cholecystobiliary fistula can also erode through the gallbladder wall into adjacent bowel — most commonly the duodenum (cholecystoduodenal fistula, MC ^[2])
• Once the fistula exists, a large gallstone can pass from the gallbladder through the fistula into the bowel lumen. If the stone is large enough ( > 2–2.5 cm), it impacts at the narrowest part of the small bowel — the terminal ileum, 2 feet proximal to the ileocaecal valve ^[2] — causing mechanical small bowel obstruction: gallstone ileus
• Bouveret's syndrome: stone stuck at the duodenum/stomach, causing gastric outlet obstruction ^[2]
• Imaging findings: Rigler's triad on AXR: pneumobilia + SBO + ectopic gallstone ^[2]
  • Pneumobilia (air in the biliary tree) occurs because the cholecystoenteric fistula allows bowel gas to reflux into the biliary system
• Management: Enterolithotomy to relieve SBO — proximal enterotomy (NOT over the stone because of ulceration) → milk the stone proximally for extraction → same-session or elective cholecystectomy + fistula repair ^[2]

5. Acute Cholangitis and Biliary Sepsis

• Mechanism: CHD obstruction → bile stasis → bacterial colonisation of stagnant bile → ascending infection. Common organisms: E. coli, Klebsiella, anaerobes. The liver's Kupffer cells normally clear gut-derived endotoxins from the portal blood, but in biliary obstruction, this function is impaired → endotoxaemia ^[3].
• Presentation: Charcot's triad (fever + jaundice + RUQ pain) in ~50–70% of cholangitis cases. If untreated → suppurative cholangitis with Reynolds' pentad (Charcot's + hypotension + altered mental status) in < 10% — a life-threatening emergency ^[7]
• Why it matters: Cholangitis is the most common acute complication requiring emergency intervention (RAD: Resuscitate → Antibiotics → Drainage) ^[16]

6. Acute Cholecystitis

• Up to 1/3 of patients with Mirizzi syndrome have acute cholecystitis on presentation ^[1]
• Mechanism: The same stone impaction at Hartmann's pouch that compresses the CHD also obstructs gallbladder outflow → bile stasis within the GB → chemical inflammation (first 48 hours) → secondary bacterial infection ^[6]
• Can progress to: gallbladder empyema (pus-filled GB), gangrenous cholecystitis (wall necrosis from ischaemia), perforation (necrotic wall ruptures → biliary peritonitis) ^[6]

7. Acute Pancreatitis

• In rare cases, acute pancreatitis can complicate Mirizzi syndrome ^[1]
• Mechanism: If the stone at Hartmann's pouch is large enough or positioned low enough, or if smaller stones migrate distally, they can obstruct the ampulla of Vater or pancreatic duct → impaired pancreatic enzyme drainage → premature intra-acinar enzyme activation → autodigestion → acute pancreatitis
• This is the same mechanism as gallstone pancreatitis from choledocholithiasis

8. Hepatic Abscess

• Mechanism: Prolonged biliary obstruction + cholangitis → ascending infection into intrahepatic ducts → suppuration → hepatic abscess formation ^[24]. This is more likely with delayed diagnosis or inadequate drainage.
• Listed as a complication of gallstones perforating to the liver ^[24]

9. Secondary Biliary Cirrhosis

• Mechanism: Long-standing, unrelieved biliary obstruction → chronic cholestasis → periductal fibrosis → progressive hepatic fibrosis → biliary cirrhosis. This is a rare long-term complication seen in delayed or missed diagnosis.

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B. Systemic Complications of Prolonged Biliary Obstruction

These are the consequences of obstructive jaundice itself, applicable to any cause of obstruction but directly relevant to Mirizzi syndrome. They are also the reasons why preoperative optimisation is critical ^[3].

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C. Complications of Treatment

C1. Complications of ERCP

ERCP is used for preoperative biliary decompression (stenting) and fistula assessment. It carries a recognised complication profile ^[23][17]:

C2. Complications of Surgery (Cholecystectomy ± Bile Duct Reconstruction)

Surgery for Mirizzi syndrome is inherently more complex and higher risk than routine cholecystectomy because of the dense inflammation, distorted anatomy, and potential need for bile duct reconstruction.

Immediate (intraoperative):

Early (postoperative, days to weeks):

Late (weeks to months to years):

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Summary: Complications Organised by Category

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Active Recall - Complications of Mirizzi Syndrome

1. Explain the mechanism by which Mirizzi syndrome predisposes to gallbladder carcinoma. What is the reported coexistence rate?

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Chronic inflammation from the impacted stone causes recurrent cycles of mucosal injury, regeneration, and fibrosis, driving a dysplasia-carcinoma sequence (analogous to UC causing CRC). Combined with biliary stasis, reactive oxygen species and DNA damage promote malignant transformation. The coexistence rate is 5-28%. Must always exclude with CT, MRCP (T2 differentiates inflammatory vs neoplastic mass), and intraoperative frozen section.

2. What is Rigler's triad? In which complication of Mirizzi syndrome would you see it, and what is the pathological explanation for each component?

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Rigler's triad = pneumobilia + small bowel obstruction + ectopic gallstone on imaging. Seen in gallstone ileus (Csendes Type 5B). Pneumobilia: cholecystoenteric fistula allows bowel gas to reflux into biliary tree. SBO: large gallstone passes through fistula and impacts at terminal ileum (narrowest part of small bowel, 2 feet proximal to ileocaecal valve). Ectopic gallstone: the stone is visible in the bowel (usually RIF area) on AXR or CT.

3. Why is bile duct injury the most feared surgical complication in Mirizzi syndrome? What anatomical factors make it more likely?

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Dense adhesions and edematous inflammatory tissue from chronic inflammation distort normal anatomy in Calot's triangle, fusing the CHD, cystic duct, and cystic artery into an unrecognisable mass. The surgeon may inadvertently clip, divide, or cauterise the CHD or right hepatic duct. The critical view of safety is often unachievable. If CHD is transected, repair requires major Roux-en-Y hepaticojejunostomy with long-term stricture risk. Conversion rates to open surgery are 30-60%.

4. Name 3 systemic complications of prolonged biliary obstruction in Mirizzi syndrome and explain the mechanism for each.

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(1) Coagulopathy/bleeding tendency: no bile salts in gut leads to malabsorption of fat-soluble vitamin K, which is a cofactor for factors II, VII, IX, X synthesis. (2) Immunocompromise/biliary sepsis: obstructed liver cannot clear gut endotoxins (impaired Kupffer cell function) plus impaired cell-mediated immunity. (3) Poor wound healing: impaired hepatic protein synthesis (reduced albumin and structural proteins) leading to poor tissue repair and anastomotic leak risk.

5. What is the most common complication of ERCP performed for Mirizzi syndrome? How does it occur and how is it prevented?

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Post-ERCP pancreatitis (incidence ~2%, most frequent ERCP complication). Occurs due to manipulation/trauma of the pancreatic orifice during biliary cannulation, causing pancreatic duct oedema and impaired drainage, leading to premature enzyme activation and autodigestion. Prevention: prophylactic pancreatic duct stent placement, guidewire-guided cannulation (avoiding contrast injection into pancreatic duct), rectal NSAIDs (indomethacin/diclofenac).

6. What is the most common long-term complication after Roux-en-Y hepaticojejunostomy performed for Csendes Type IV Mirizzi syndrome? How does it present?

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Stenosis (stricture) of the biliary-enteric anastomosis. Caused by scarring and fibrosis at the hepaticojejunostomy site. Presents with recurrent obstructive jaundice, cholangitis, and if prolonged, secondary biliary cirrhosis. Managed by percutaneous/endoscopic balloon dilatation and stenting, or revision hepaticojejunostomy if refractory.

References

^[1] Senior notes: felixlai.md (Mirizzi syndrome overview, classification, treatment, pp. 572–575) ^[2] Senior notes: maxim.md (Mirizzi syndrome definition, classification, management, gallstone ileus, pp. 131–132) ^[3] Lecture slides: Malignant biliary obstruction.pdf (Manifestations of pathophysiological disturbance of MBO: bleeding tendency, infection, poor wound healing) ^[6] Senior notes: maxim.md (Acute calculous cholecystitis pathogenesis and complications, p. 131) ^[7] Senior notes: felixlai.md (Acute cholangitis clinical manifestation — Charcot's/Reynolds', p. 521) ^[16] Senior notes: maxim.md (Acute cholangitis management — RAD; long-term complications after LC, pp. 135–136) ^[17] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (ERCP complications — perforation, bleeding from papillotomy, pancreatitis, p. 14) ^[21] Senior notes: maxim.md (Cholecystectomy complications — immediate, early, late, pp. 133–134) ^[23] Senior notes: felixlai.md (ERCP complications table, p. 89) ^[24] Senior notes: felixlai.md (Complications of gallstones — in gallbladder, bile duct, perforation to other sites, pp. 518–519) ^[25] Senior notes: felixlai.md (Roux-en-Y hepatojejunostomy — most frequent long-term complication is anastomotic stenosis, p. 543)