Biliary Cysts

1. Definition

Biliary cysts are congenital cystic dilatations that can occur singly or multiply throughout the biliary tree — both intrahepatic and extrahepatic bile ducts ^[1][2].

• The term "choledochal cyst" was coined in 1959, originally referring only to extrahepatic bile duct dilatations ^[1].
  • "Choledocho-" = common bile duct (Greek: choledochos = "receiving bile"); "cyst" = fluid-filled sac (Greek: kystis = bladder/sac).
  • So the name literally means "a cystic sac of the common bile duct."
• The nomenclature was expanded in 1977 to include intrahepatic cysts and further refined in 2003 to incorporate the concept of an abnormal pancreaticobiliary junction (APBJ) ^[1].
• The modern umbrella term "biliary cyst" is preferred because it captures the full spectrum — extrahepatic, intrahepatic, or both.

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2. Epidemiology

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3. Anatomy and Function of the Biliary System (Foundation)

To understand biliary cysts, you must first understand the normal anatomy they distort.

3.1 Normal Biliary Anatomy

• Intrahepatic bile ducts → drain bile produced by hepatocytes.
• Right and Left Hepatic Ducts → join at the hilum to form the Common Hepatic Duct (CHD).
• CHD + Cystic Duct → form the Common Bile Duct (CBD) (~7–8 cm long, < 6 mm diameter normally).
• CBD + Main Pancreatic Duct → enter the duodenum at the Ampulla of Vater, surrounded by the Sphincter of Oddi.

3.2 Normal Pancreaticobiliary Junction

• The CBD and pancreatic duct normally join within the duodenal wall (intramural segment), forming a very short common channel (< 5 mm) controlled by the Sphincter of Oddi.
• The Sphincter of Oddi prevents reflux of duodenal content and pancreatic juice into the biliary tree.

3.3 Function of the Biliary Tree

• Transports bile (containing bile salts, bilirubin, cholesterol, phospholipids) from the liver to the duodenum for fat digestion and waste excretion.
• The gallbladder stores and concentrates bile between meals.

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4. Etiology

4.1 Congenital vs. Acquired

Biliary cysts can be congenital (the vast majority) or rarely acquired ^[1].

4.2 The Central Aetiological Theory: Abnormal Pancreaticobiliary Junction (APBJ)

This is the dominant aetiological concept you must understand:

APBJ is present in 70–90% of patients with biliary cysts ^[1].

What is APBJ?

• APBJ = the pancreatic duct joins the CBD > 1 cm proximal to the Ampulla of Vater (i.e., outside the duodenal wall) ^[1].
• This creates a long common channel that lies outside the regulatory influence of the Sphincter of Oddi.

Why does APBJ cause biliary cysts?

The pathophysiology is elegant and logical:

1. Loss of sphincteric control → The Sphincter of Oddi normally prevents reflux. When the junction is proximal (outside the duodenal wall), the sphincter cannot control the long common channel.
2. Pancreatic juice reflux into the biliary tree → Pancreatic enzymes (lipase, phospholipase A₂, trypsin, elastase) are activated and directly contact biliary epithelium.
3. Chemical damage to biliary epithelium → Chronic inflammation, epithelial destruction, and weakening of the bile duct wall.
4. Cystic dilatation → The weakened, inflamed bile duct wall progressively dilates under normal intraluminal pressure → forming a cyst.
5. Malignant transformation → Chronic inflammation and epithelial turnover → metaplasia → dysplasia → cholangiocarcinoma.

Congenital Embryological Theory (Supplementary)

• During embryological development, the biliary epithelium undergoes a solid cord phase followed by recanalization (vacuolization).
• Congenital cysts may result from unequal proliferation of embryologic biliary epithelial cells before bile duct canalization is complete ^[1].
• This leads to areas of ductal weakness and dilatation.

4.3 Hong Kong / Asian Context

In Hong Kong and East Asia, biliary cysts are significantly more common than in the West. Relevant associations include:

• APBJ — more common in Asian populations (genetic/developmental predisposition) ^[1].
• Parasitic infection (Clonorchis sinensis — transmitted by consumption of raw/undercooked freshwater fish 淡水魚) — causes chronic biliary inflammation that may synergistically worsen outcomes in patients with pre-existing biliary cysts ^[3][4].
• Recurrent pyogenic cholangitis (RPC) (the "Hong Kong disease") — shares overlapping pathology with biliary cysts (intrahepatic stone formation, stricturing, biliary stasis) ^[4].

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5. Classification: Todani Classification (Modified Alonso-Lej)

This is the universally used classification system. Most commonly Type I ^[2].

5.1 Caroli Disease vs. Caroli Syndrome

• Think of Caroli syndrome as the more severe form on a disease spectrum — biliary cysts + hepatic fibrosis + renal cysts.
• "Caroli" — named after Jacques Caroli, French gastroenterologist who described the condition.

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6. Pathophysiology — Consequences of Biliary Cysts

Understanding the pathophysiology of biliary cysts explains every clinical feature and complication:

6.1 Biliary Stasis

• Cystic dilatation creates a "sump" where bile pools and stagnates instead of flowing freely to the duodenum.
• Consequence: Stone formation (choledocholithiasis), bacterial colonization, cholangitis.

6.2 Reflux of Pancreatic Juice (via APBJ)

• Activated pancreatic enzymes continuously damage the cyst epithelium.
• Consequence: Chronic inflammation, epithelial hyperplasia, malignant transformation.

6.3 Chronic Inflammation → Malignant Transformation

• The cyst epithelium undergoes a metaplasia–dysplasia–carcinoma sequence analogous to Barrett's oesophagus.
• Risk of cholangiocarcinoma:
  • Overall lifetime risk: 10–30% in untreated biliary cysts.
  • Risk increases with age (especially after 20 years of age).
  • Highest in Type I and Type IVa cysts.
  • Also elevated in patients with APBJ even without overt cystic dilatation.

6.4 Obstruction

• Cysts can compress adjacent structures (CBD, hepatic ducts, portal vein).
• Consequence: Obstructive jaundice, secondary biliary cirrhosis (if chronic), portal hypertension.

6.5 Infection

• Stagnant bile is an excellent culture medium.
• Consequence: Recurrent cholangitis, liver abscess.

6.6 Pancreatitis

• In APBJ, the long common channel allows not only pancreatic-to-biliary reflux but also biliary-to-pancreatic reflux.
• Bile reflux into the pancreatic duct → activation of pancreatic enzymes within the pancreas → acute pancreatitis.

6.7 Rupture (Rare)

• Thin-walled cysts (especially in neonates) can rupture, leading to bile peritonitis.

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7. Clinical Features

7.1 Presentation by Age Group

7.2 Symptoms

Classic triad: Jaundice + Abdominal pain + Abdominal mass ^[1][2]

The classic triad is present in only about 20–30% of adults but is more common in children. Don't rely on the full triad for diagnosis.

7.3 Signs

7.4 Presentation in Neonates

• May present with obstructive jaundice mimicking biliary atresia.
• Palpable abdominal mass.
• Acholic (pale) stools + dark urine.
• Must differentiate from biliary atresia — imaging (USG → MRCP) is essential.

7.5 Clinical Features by Type

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8. Key Associations and Related Conditions

8.1 Biliary Cysts and Cholangiocarcinoma

This is the most critical association:

• Associated with increased risk of cholangiocarcinoma (CC) especially patients with Type I and IV biliary cysts and those with APBJ ^[1][3].
• Fibrocystic liver disease leads to cholangiocarcinoma by biliary stasis, chronic inflammation from reflux of pancreatic juice, abnormalities in bile salt transporter proteins resulting in unstable bile content or deconjugation of carcinogens previously conjugated in the liver ^[3].
• Risk increases with age — this is why prophylactic surgical excision is recommended even in asymptomatic patients.
• The malignancy can arise within the cyst itself or in any part of the biliary tree (including residual bile duct after incomplete excision).

8.2 Biliary Cysts as a Risk Factor for Gallbladder Cancer

• Choledochal cysts and abnormal pancreaticobiliary tract are listed as risk factors for gallbladder carcinoma ^[5].
• This is because APBJ affects the entire biliary epithelium, including the gallbladder.

8.3 Biliary Cysts and Recurrent Pyogenic Cholangitis (RPC)

• Biliary cysts (especially Type IVa and V) share pathological features with RPC: intrahepatic dilatation, stricturing, and stone formation ^[4].
• In Hong Kong, biliary cysts and RPC can co-exist, particularly with Clonorchis sinensis infection.

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9. Summary Table: Biliary Cysts at a Glance

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Active Recall - Biliary Cysts (Definition, Epidemiology, Aetiology, Classification, Clinical Features)

1. What is an abnormal pancreaticobiliary junction (APBJ) and how does it lead to biliary cyst formation and cholangiocarcinoma?

Your answer

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APBJ = pancreatic duct joins CBD more than 1 cm proximal to Ampulla of Vater, outside sphincter of Oddi control. Creates long common channel allowing reflux of pancreatic juice into biliary tree. Activated enzymes damage biliary epithelium causing chronic inflammation, wall weakening, and cystic dilatation. Chronic inflammation drives metaplasia-dysplasia-carcinoma sequence leading to cholangiocarcinoma. Present in 70-90% of biliary cyst patients.

2. List the Todani classification types and state which is the most common and which carries the highest malignancy risk.

Your answer

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Type I: extrahepatic CBD dilatation (most common, 50-80%). Type II: extrahepatic diverticulum. Type III: choledochocele (intraduodenal, lowest malignancy risk). Type IVa: intra + extrahepatic cysts. Type IVb: multiple extrahepatic. Type V: Caroli disease (intrahepatic only). Highest malignancy risk: Types I and IVa.

3. What is the classic triad of biliary cysts and what is the pathophysiological basis for each component?

Your answer

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Triad: jaundice (biliary obstruction causing conjugated hyperbilirubinaemia), abdominal pain (cyst wall distension, cholangitis, pancreatitis, or stone formation), and abdominal mass (large palpable cyst, especially Type I in children). Present in only 20-30% of adults.

4. Distinguish between Caroli disease and Caroli syndrome.

Your answer

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Caroli disease = Type V biliary cyst = multiple saccular dilatations of intrahepatic bile ducts only. Caroli syndrome = Caroli disease PLUS congenital hepatic fibrosis, strongly associated with ARPKD, may cause portal hypertension. Both autosomal recessive, PKHD1 gene mutation.

5. A 25-year-old woman in Hong Kong presents with recurrent RUQ pain, intermittent jaundice, and episodes of fever. USG shows fusiform dilatation of the CBD with intrahepatic duct dilatation. What is the most likely diagnosis, and what definitive management would you recommend and why?

Your answer

Grade

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Type IVa biliary cyst (Todani classification). Definitive management: radical excision of the cyst with Roux-en-Y hepaticojejunostomy. Rationale: prevent cholangiocarcinoma (10-30% lifetime risk), reduce recurrent cholangitis and stricture risk. Simple drainage or cyst-enterostomy is inadequate because residual cyst epithelium retains malignant potential.

References

^[1] Senior notes: felixlai.md (Biliary cysts section) ^[2] Senior notes: maxim.md (Choledochal cyst section) ^[3] Senior notes: felixlai.md (Cholangiocarcinoma etiology section) ^[4] Senior notes: maxim.md (Recurrent pyogenic cholangitis section); felixlai.md (RPC section) ^[5] Senior notes: felixlai.md (Gallbladder cancer risk factors section); maxim.md (Gallbladder carcinoma section)

Differential Diagnosis of Biliary Cysts

The differential diagnosis of a biliary cyst revolves around a fundamental clinical question: what else can cause cystic/dilated structures in or around the biliary tree, or produce the same symptom complex (jaundice + RUQ pain + abdominal mass)?

To reason through this systematically, let's think about what biliary cysts actually look like to the clinician and on imaging:

1. On imaging: A cystic dilatation of the bile duct (intra- or extrahepatic).
2. Clinically: Some combination of obstructive jaundice, RUQ pain, palpable mass, cholangitis, and/or pancreatitis.

We must therefore differentiate biliary cysts from conditions that mimic either their imaging appearance or their clinical presentation — or both.

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Organising Framework

I find it most useful to split the differential into two axes:

A. Conditions that mimic cystic biliary dilatation on imaging (the "what else could that cyst be?" question).

B. Conditions that present with a similar clinical syndrome (jaundice ± RUQ pain ± mass ± cholangitis).

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A. Conditions Mimicking Cystic Biliary Dilatation on Imaging

These are conditions that can look like a "cyst" in the biliary region on USG, CT, or MRCP:

1. Biliary Atresia (Neonatal DDx)

• Why it mimics: In neonates, both biliary atresia and biliary cysts present with prolonged neonatal jaundice, dark urine, and pale stools ^[6]. On USG, biliary atresia shows a contracted gallbladder and triangular cord sign (fibrous remnant of extrahepatic duct), which must be distinguished from a dilated cystic duct in choledochal cyst ^[6].
• How to differentiate:
  • Biliary atresia → no visible bile ducts / small/absent gallbladder / triangular cord sign at porta hepatis.
  • Biliary cyst → visible cystic dilatation of the bile duct; gallbladder often present.
  • E-HIDA scan (hepatobiliary iminodiacetic acid): In biliary atresia, there is absence of isotope in the intestine (no biliary excretion). In biliary cyst, isotope accumulates in the cyst and may still reach the intestine (unless completely obstructed) ^[6].
  • Operative cholangiogram is the gold standard for biliary atresia ^[6].

2. Pancreatic Cyst / Pseudocyst

• Why it mimics: A cyst in the head of the pancreas (e.g., intraductal papillary mucinous neoplasm (IPMN), mucinous cystic neoplasm, serous cystadenoma, or pseudocyst) can be adjacent to or compress the distal CBD, mimicking a distal choledochal cyst (Type III) on imaging ^[7].
• How to differentiate:
  • Pancreatic pseudocyst: History of pancreatitis, thick wall, no epithelial lining (hence "pseudo-"), arises from pancreatic parenchyma not from the bile duct wall.
  • IPMN: Communicates with the pancreatic duct (not the bile duct), seen on MRCP as grape-like cystic dilatations of the pancreatic duct.
  • MRCP clearly delineates whether the cyst arises from the biliary tree or the pancreatic duct ^[2].

3. Hepatic Cyst (Simple Cyst / Hydatid Cyst)

• Why it mimics: Simple hepatic cysts are extremely common and can be located near the hilum, mimicking intrahepatic biliary cysts (Type IVa or V). Hydatid cysts (Echinococcus granulosus) can also appear as large cystic structures in the liver.
• How to differentiate:
  • Simple hepatic cysts: Do not communicate with the biliary tree. On MRCP, there is no connection to bile ducts. Thin-walled, anechoic on USG.
  • Hydatid cysts: May show daughter cysts, membrane detachment ("water lily sign"), or calcification. Echinococcus serology positive. Travel history (sheep-farming regions).
  • Biliary cysts (Type V / Caroli): Directly communicate with intrahepatic bile ducts — this is the key distinguishing feature on MRCP. May show the "central dot sign" on CT (portal vein radicle surrounded by dilated duct).

4. Biliary Cystadenoma / Cystadenocarcinoma

• Why it mimics: These are rare true neoplastic cysts of the biliary epithelium. They appear as large, multiloculated cystic masses within the liver, mimicking Type IVa or V biliary cysts.
• How to differentiate:
  • Cystadenoma: Multiloculated with internal septae, mural nodules, mucin-secreting epithelium. Predominantly in middle-aged women.
  • On MRCP: Does not show the saccular ductal communication pattern of Caroli disease.
  • Biopsy/resection shows ovarian-type stroma (in the mucinous subtype).
  • Key point: Any biliary cyst with mural nodularity or solid components should raise concern for cystadenoma/cystadenocarcinoma or malignant transformation within a choledochal cyst.

5. CBD Dilatation from Distal Obstruction (Not a True Cyst)

• Why it mimics: Any cause of distal CBD obstruction (choledocholithiasis, pancreatic head carcinoma, periampullary carcinoma, chronic pancreatitis) can cause upstream CBD dilatation that may look fusiform, mimicking a Type I biliary cyst ^[8][9].
• How to differentiate:
  • Age: Biliary cysts are congenital and typically present in young patients; malignant obstruction presents in the elderly.
  • Imaging: In distal obstruction, the dilatation tapers to a point of obstruction (the "cut-off" sign). In a true biliary cyst, the cyst has a defined wall and the duct calibre changes abruptly at the cyst margins.
  • APBJ: Present in biliary cysts (70–90%), absent in reactive dilatation.
  • CBD > 8 mm on USG suggests dilatation ^[9]; but true biliary cysts are typically much larger and more globular.
  • Post-cholecystectomy or post-ERCP sphincterotomy can cause mild CBD dilatation (up to 10 mm) that is physiological, not a cyst ^[4].

6. Duodenal Duplication Cyst

• Why it mimics: A duplication cyst of the second part of the duodenum can appear adjacent to the distal CBD and mimic a Type III choledochal cyst (choledochocele).
• How to differentiate:
  • Duplication cyst: Has a muscular wall with intestinal mucosa. Does not communicate with the bile duct on MRCP.
  • Choledochocele: Communicates with the CBD and protrudes into the duodenal lumen.
  • EUS (endoscopic ultrasound) can distinguish the layers of the cyst wall.

7. Gallbladder Hydrops / Mucocele

• Why it mimics: A massively distended gallbladder (hydrops from cystic duct obstruction) can appear as a large cystic RUQ mass, mimicking a large Type I choledochal cyst on quick USG assessment.
• How to differentiate:
  • Hydrops: The cyst is clearly the gallbladder (connects to cystic duct, fundus projects inferiorly). Contains mucoid/clear fluid. Cystic duct stone may be visible.
  • Biliary cyst: The cyst is the bile duct itself; the gallbladder is a separate structure.
  • MRCP unambiguously resolves this.

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B. Conditions Mimicking the Clinical Syndrome

These conditions produce overlapping symptoms (jaundice, RUQ pain, fever, mass) but are NOT cystic dilatations of the bile duct:

1. Choledocholithiasis (CBD Stone) [9]

2. Acute Cholangitis [3]

• Presents with Charcot's triad: fever + jaundice + RUQ pain (present in ~2/3 of patients) ^[3].
• However, acute cholangitis is a complication of biliary cysts, not an alternative diagnosis. If a young patient presents with cholangitis, always ask: why is this young person getting cholangitis? — and consider an underlying biliary cyst or APBJ.

3. Acute Cholecystitis [10]

• Presents with RUQ pain, fever, positive Murphy's sign.
• Distinguished from biliary cysts by: USG showing gallbladder wall thickening (> 3 mm), pericholecystic fluid, gallstones in GB. The bile duct itself is not cystically dilated.
• Pain > 6 hours (vs. biliary colic < 6 hours) ^[10].

4. Mirizzi Syndrome [11]

• CHD obstruction caused by extrinsic compression from an impacted stone in Hartmann's pouch/cystic duct ^[11].
• Can present with jaundice + RUQ pain + palpable gallbladder (an exception to Courvoisier's Law) ^[11].
• How to differentiate from biliary cyst:
  • Mirizzi: Gallstone impacted in cystic duct/Hartmann's pouch with external compression of CHD. USG shows dilatation above the level of gallbladder neck with abrupt change to normal CBD below ^[11].
  • Biliary cyst: Intrinsic cystic dilatation of the bile duct itself. No impacted stone in the cystic duct.
  • MRCP resolves the distinction definitively.

5. Cholangiocarcinoma [3][5]

• Cholangiocarcinoma is a complication of biliary cysts (10–30% lifetime risk) but also enters the DDx when a biliary cyst patient develops new symptoms.
• Perihilar cholangiocarcinoma (Klatskin tumour) can cause hilar stricturing that mimics a biliary cyst on initial imaging ^[5].
• Red flags for malignant transformation within a known biliary cyst: New-onset weight loss, progressive painless jaundice, rising CA 19-9, solid mural nodules within the cyst on imaging.
• Risk factors for cholangiocarcinoma include: PSC, RPC, choledochal cysts, Caroli's disease, Lynch syndrome, Clonorchis sinensis, Thorotrast ^[5].

6. Recurrent Pyogenic Cholangitis (RPC) [4]

• "Hong Kong disease" — recurrent bacterial cholangitis with intrahepatic pigment stones and intrahepatic biliary obstruction (strictures) ^[4].
• Shares features with biliary cysts: intrahepatic ductal dilatation, recurrent cholangitis, left lobe predilection.
• How to differentiate:
  • RPC: Acquired condition. Intrahepatic stone disease with stricture-dilatation pattern. Brown pigment stones formed de novo in bile ducts. Left intrahepatic ducts predominantly. Middle-aged onset. History of parasitic exposure.
  • Biliary cyst: Congenital. Defined cystic dilatation. APBJ present. Presents younger.
  • CT in RPC: Central dilated bile ducts with peripheral tapering, left lobe predilection, liver atrophy ^[4].

7. Primary Sclerosing Cholangitis (PSC) [12]

• Chronic progressive disorder characterized by inflammation, fibrosis and stricturing of bile ducts ^[12].
• Can cause intrahepatic and extrahepatic ductal changes that mimic biliary cysts on imaging.
• How to differentiate:
  • PSC: Strong association with ulcerative colitis. Shows "beading" pattern (alternating strictures and dilatations) on MRCP. p-ANCA positive. No APBJ. Middle-aged males.
  • Biliary cyst: Congenital. Discrete cystic dilatation (not beading). APBJ present. Young females.

8. Primary Biliary Cholangitis (PBC) [13]

• Autoimmune destruction of small intralobular bile ducts → chronic cholestasis ^[13].
• Presents with pruritus, fatigue, cholestatic LFTs.
• Distinguished from biliary cysts by: AMA positive, no cystic dilatation on imaging, extreme female predominance (90–95%), middle-aged.

9. Pancreatic Head Carcinoma [14]

• Painless progressive obstructive jaundice in the elderly is malignant biliary obstruction until proven otherwise ^[8].
• Can cause dilated CBD mimicking Type I biliary cyst.
• Distinguished by: age (elderly), weight loss, Courvoisier's sign positive (palpable non-tender gallbladder in painless jaundice) ^[14], pancreatic mass on CT, CA 19-9 elevated.

10. Liver Abscess [3][11]

• Pyogenic or amoebic liver abscess can appear as a cystic hepatic lesion on USG.
• Distinguished by: fever, leukocytosis, elevated inflammatory markers, thick irregular wall with internal debris (not clear fluid), no communication with bile ducts.
• Listed as a differential for infected choledochal cysts ^[3].

11. Acute Pancreatitis [1]

• Biliary cysts with APBJ can present with pancreatitis. Conversely, pancreatitis from any cause can produce a pseudocyst that mimics a biliary cyst.
• Elevated serum amylase/lipase, clinical context, and MRCP showing the origin of the cyst (bile duct vs. pancreas) differentiate the two.

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Summary Differential Diagnosis Table

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High Yield: The most important differential in neonates is biliary atresia (Kasai procedure needed within 60 days). The most important differential in adults is malignant transformation within the cyst (cholangiocarcinoma) or malignant biliary obstruction mimicking a cyst. Always think: is this a true congenital cyst, or reactive dilatation from obstruction?

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Active Recall - Differential Diagnosis of Biliary Cysts

1. A neonate presents with prolonged conjugated jaundice, pale stools, and dark urine. USG shows a cystic structure at the porta hepatis. What are the two most important surgical diagnoses to differentiate and how would you distinguish them?

Your answer

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Biliary atresia vs choledochal cyst. Biliary atresia: contracted/absent GB, triangular cord sign at porta hepatis, absence of isotope in intestine on HIDA scan. Choledochal cyst: visible cystic dilatation of bile duct, GB usually present, isotope accumulates in cyst on HIDA. Operative cholangiogram is gold standard for biliary atresia. Key urgency: Kasai procedure needed within 60 days for biliary atresia.

2. How would you differentiate Caroli disease (Type V biliary cyst) from simple hepatic cysts and hydatid cysts on imaging?

Your answer

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Caroli disease: intrahepatic cystic dilatations that COMMUNICATE with the biliary tree on MRCP; central dot sign on CT (portal vein radicle surrounded by dilated duct). Simple hepatic cyst: NO communication with bile ducts, thin-walled, anechoic, asymptomatic. Hydatid cyst: daughter cysts, water lily sign, membrane detachment, calcification; positive Echinococcus serology; no biliary communication unless ruptured into ducts.

3. An elderly patient presents with painless progressive jaundice. USG shows a dilated CBD. How do you differentiate this from a Type I biliary cyst?

Your answer

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Age (elderly vs young); in distal obstruction the CBD tapers to a point of obstruction (cut-off sign) whereas a true cyst has a defined cyst wall with abrupt calibre change; Courvoisier sign positive in malignant obstruction (palpable non-tender GB) but negative in congenital cyst; no APBJ in reactive dilatation; CT/MRCP shows pancreatic mass or periampullary tumour in malignant obstruction; painless progressive obstructive jaundice in elderly is malignant until proven otherwise.

4. A young woman in Hong Kong presents with recurrent cholangitis and intrahepatic ductal dilatation with stricturing, predominantly in the left lobe. What are the two main differential diagnoses and how do you distinguish them?

Your answer

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Biliary cyst (Type IVa or V) vs Recurrent Pyogenic Cholangitis (RPC). RPC: acquired, middle-age onset, intrahepatic pigment stones formed de novo, stricture-dilatation pattern, left lobe predilection, brown pigment stones, associated with Clonorchis sinensis. Biliary cyst: congenital, presents younger, defined cystic dilatation (not stricture-dilatation), APBJ present in 70-90%. CT in RPC shows central dilated ducts with peripheral tapering and liver atrophy.

5. Name three conditions where cystic or dilated biliary structures on imaging represent acquired pathology rather than a congenital biliary cyst.

Your answer

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Any three of: (1) CBD dilatation from distal obstruction (choledocholithiasis, pancreatic head CA, periampullary CA); (2) Pancreatic pseudocyst compressing/adjacent to CBD; (3) Post-cholecystectomy or post-ERCP physiological CBD dilatation; (4) RPC with stricture-dilatation pattern; (5) PSC with beading pattern. Key principle: acquired dilatation has identifiable cause and no APBJ.

References

^[1] Senior notes: felixlai.md (Biliary cysts section) ^[2] Senior notes: maxim.md (Choledochal cyst section) ^[3] Senior notes: felixlai.md (Acute cholangitis section) ^[4] Senior notes: maxim.md (Recurrent pyogenic cholangitis section); felixlai.md (RPC section) ^[5] Senior notes: maxim.md (Cholangiocarcinoma section); felixlai.md (Cholangiocarcinoma section) ^[6] Senior notes: maxim.md (Hepatobiliary conditions — paediatric section) ^[7] Senior notes: maxim.md (Pancreatic cyst section) ^[8] Lecture slides: Malignant biliary obstruction.pdf; Senior notes: maxim.md (Obstructive jaundice section) ^[9] Senior notes: maxim.md (Choledocholithiasis section); felixlai.md (Choledocholithiasis section) ^[10] Senior notes: maxim.md (Acute cholecystitis section); felixlai.md (Acute cholecystitis section) ^[11] Senior notes: maxim.md (Mirizzi syndrome section); felixlai.md (Mirizzi syndrome section) ^[12] Senior notes: felixlai.md (Primary sclerosing cholangitis section) ^[13] Senior notes: felixlai.md (Primary biliary cholangitis section) ^[14] Senior notes: felixlai.md (Pancreatic cancer section)

Diagnostic Criteria for Biliary Cysts

Unlike conditions such as acute cholangitis (which has codified Tokyo Guidelines criteria) or acute cholecystitis (Tokyo criteria with defined scoring), biliary cysts do not have a formal "diagnostic criteria" scoring system. The diagnosis is primarily imaging-based, supported by clinical context and biochemistry.

That said, the diagnosis of a biliary cyst requires establishing three things:

1. Presence of a cystic dilatation that communicates with the biliary tree.
2. Classification of the cyst type (Todani).
3. Assessment for APBJ and exclusion of malignancy.

Let me walk you through the diagnostic approach logically, from bedside to operating theatre.

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Diagnostic Algorithm

The approach follows a stepwise logic: Clinical suspicion → Bloods → Initial imaging (USG) → Definitive imaging (MRCP) → Pre-operative planning (CT ± ERCP) → Operative confirmation.

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Investigation Modalities — Detailed Breakdown

1. Biochemical Tests (Blood Investigations)

Blood tests in biliary cysts are often normal in uncomplicated cases. They become abnormal when there are complications (cholangitis, pancreatitis, malignancy). Here is what to order and why:

a) CBC with Differentials [1]

b) Liver Function Tests (LFT) [1][15]

Why does obstructive jaundice cause a cholestatic pattern? Because ALP and GGT are enzymes located on the biliary canalicular membrane. When bile cannot flow (obstruction), there is back-pressure on the canaliculi, inducing synthesis and release of these enzymes into the bloodstream. This is fundamentally different from hepatocellular damage (where AST/ALT are released from damaged hepatocytes).

c) Clotting Profile (PT/INR) [15]

d) Serum Amylase / Lipase [1]

e) Tumour Markers [15]

f) Additional Bloods (if indicated)

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2. Radiological Investigations

This is the core of biliary cyst diagnosis. Let me walk through each modality in the logical order you'd use clinically:

a) Transabdominal Ultrasound (USG) — Initial diagnostic modality [2]

Why USG first?

• Non-invasive, no radiation, no contrast, readily available, cheap, can be done at bedside.
• Excellent for detecting biliary dilatation and gallstones.

Key Findings in Biliary Cysts:

Limitations of USG ^[1]:

• Results affected by patient's body habitus, presence of bowel gas, and limited visualisation due to overlying structures ^[1].
• Frequently misses Type III choledochal cysts ^[1] — because the choledochocele is located in the intraduodenal (intramural) segment of the distal CBD, which is deep in the retroperitoneum behind the duodenum, where bowel gas obscures the view.
• Cannot reliably demonstrate APBJ.
• Cannot fully characterise intrahepatic disease (Type IVa, V).
• Operator-dependent ^[10].

In neonates:

• USG is the first-line investigation for conjugated neonatal jaundice.
• Must distinguish from biliary atresia: contracted GB + triangular cord sign = biliary atresia ^[6]; cystic dilatation of bile duct = choledochal cyst ^[6].

CBD normal limits (exam pearl from senior notes): CBD limit: 0.1 cm for every 10 years old ^[17]. So a 60-year-old can have a CBD of up to 6 mm normally. Post-cholecystectomy, the CBD may dilate by 1–2 mm as the bile duct assumes a reservoir function. CBD > 8 mm is generally considered pathological ^[9][17].

b) Endoscopic Ultrasound (EUS) [1]

When to use:

• When transabdominal USG is equivocal or limited.
• When Type III (choledochocele) is suspected — EUS provides excellent visualisation of the intraduodenal distal CBD.
• To assess the cyst wall for mural nodularity or solid components (malignancy screening).
• To evaluate the pancreaticobiliary junction.

Key Advantages:

• Demonstrates extrahepatic biliary cysts and provides detailed images of the cyst wall and pancreaticobiliary junction ^[1].
• NOT limited by body habitus, bowel gas, or overlying structures ^[1].
• Can guide FNA if there is a suspicious solid component.

Limitations:

• Requires endoscopy (invasive, sedation needed).
• Cannot assess intrahepatic ducts as well as MRCP.
• EUS cannot reach the lumen of the bile duct in majority of cases ^[15] — so for detailed cholangiography, MRCP or ERCP is needed.

c) Magnetic Resonance Cholangiopancreatography (MRCP) — Test of choice [1][2]

This is the single most important investigation for biliary cysts. Let me explain why from first principles.

What is MRCP?

• Non-contrast, T2-weighted MRI sequence ^[17].
• T2-weighted images make fluid appear bright white (hyperintense). Since bile is fluid, the entire biliary tree "lights up" on T2 sequences, creating a beautiful cholangiogram without needing to inject any contrast.
• "MR" = magnetic resonance; "CP" = cholangiopancreatography ("cholangio-" = bile duct, "pancreat-" = pancreas, "-graphy" = imaging).

Why is MRCP the test of choice? ^[1]

Key MRCP Findings in Biliary Cysts:

d) CT Abdomen with Contrast — Determines extent [2][1]

When to use:

• After MRCP has confirmed and classified the cyst.
• Pre-operative planning: anatomy, extent, vascular relationships, and malignancy screening.

Key CT Findings:

Limitations:

• Radiation exposure (relevant in children — minimise if possible).
• Less detailed biliary anatomy compared to MRCP.
• Not useful for detecting gallstones (only 75% of gallstones identified on CT ^[17]).

Biliary cysts should be differentiated from cysts that do NOT communicate with the biliary tree including pancreatic, mesenteric and hepatic cysts ^[1]. This is the single most important interpretation point on imaging.

e) ERCP (Endoscopic Retrograde Cholangiopancreatography) [1][15]

What is ERCP?

• An endoscopic procedure where a duodenoscope is passed to the ampulla of Vater, the bile duct is cannulated, and contrast is injected under fluoroscopy to visualise the biliary tree.
• "Endoscopic" = via endoscope; "Retrograde" = contrast flows backwards (upstream) from the ampulla; "Cholangio-" = bile duct; "Pancreat-" = pancreas; "-graphy" = imaging.

Role in Biliary Cysts:

• Largely replaced by MRCP as a diagnostic tool ^[15].
• Still useful when:
  • Therapeutic intervention is needed: biliary stenting for cholangitis, sphincterotomy for Type III cyst.
  • Brush cytology is needed to evaluate for cholangiocarcinoma.
  • MRCP is contraindicated (e.g., MRI-incompatible implant) or equivocal.

Key Findings on ERCP:

• Cholangiogram shows the cystic dilatation and its relationship to the biliary tree.
• Can demonstrate APBJ (long common channel).
• Can identify stones within the cyst.
• Brush cytology of the cyst wall for malignant cells.

Risks of ERCP (why we prefer MRCP):

• Post-ERCP pancreatitis (3–5% risk) — contrast injection into the pancreatic duct.
• Cholangitis — introduction of bacteria into an obstructed system.
• Perforation of the duodenum or bile duct.
• Bleeding after sphincterotomy.

f) Percutaneous Transhepatic Cholangiography (PTC) [17]

When to use:

• Preferred to ERCP when obstruction is at or above the level of confluence of hepatic ducts ^[17] — because ERCP approaches from below (retrograde) and cannot easily pass proximal high-grade obstructions.
• Useful in Type IVa with high intrahepatic obstruction.
• Can be combined with percutaneous transhepatic biliary drainage (PTBD) for decompression.

Complications: Bacteraemia (thus antibiotic prophylaxis required), haemobilia ^[17].

g) Cholescintigraphy (HIDA Scan) [17][6]

What is it?

• HIDA = Hepatobiliary Iminodiacetic Acid scan. A nuclear medicine study where a technetium-99m-labelled IDA compound is injected IV, taken up by hepatocytes, and excreted into bile.
• You then image the abdomen with a gamma camera to follow the tracer through the biliary tree.

Role in Biliary Cysts:

• Primarily used in neonates to differentiate biliary cyst from biliary atresia.
• In biliary atresia: absence of isotope in the intestine ^[6] (no biliary excretion at all).
• In biliary cyst: Isotope accumulates in the cyst and may eventually reach the intestine (unless completely obstructed).
• Pre-treatment with 5 days of phenobarbitone (a liver enzyme inducer that increases biliary secretion) improves the sensitivity of the test ^[6].

h) Operative Cholangiogram [6]

• Gold standard for confirming the diagnosis in paediatric surgery settings ^[6].
• Performed intra-operatively: contrast is injected directly into the biliary tree via the cystic duct or gallbladder during surgery.
• Delineates the cyst anatomy in real-time, confirms communication with the biliary tree, identifies APBJ, and guides the extent of excision.
• Especially important in neonates where pre-operative imaging may be inconclusive.

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Summary: Investigation Algorithm — The Three-Step Approach

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3. Special Considerations

Neonatal Diagnostic Approach

In a neonate with conjugated jaundice, the diagnostic pathway is specifically designed to differentiate biliary cyst from biliary atresia as rapidly as possible:

Assessment for Malignancy Within a Known Biliary Cyst

For any patient with a known biliary cyst (especially Type I or IVa, and especially if age > 20), you must actively look for malignant transformation:

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Active Recall - Diagnosis and Investigation of Biliary Cysts

1. What is the three-step investigation approach for a suspected biliary cyst and what does each modality assess?

Your answer

Grade

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Step 1: USG (initial diagnostic modality — detect cystic dilatation, exclude gallstones). Step 2: MRCP (test of choice — confirm cyst communicates with biliary tree, classify Todani type, demonstrate APBJ, no radiation or risk of cholangitis/pancreatitis). Step 3: CT (determine extent of intrahepatic involvement, vascular anatomy, exclude malignancy — mural nodules, lymphadenopathy, metastases).

2. Why is MRCP preferred over ERCP as the primary diagnostic tool for biliary cysts?

Your answer

Grade

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MRCP is non-invasive, uses T2-weighted sequences where fluid/bile appears bright without contrast injection. Does not expose patients to ionising radiation (important in children). Does not carry risks of post-ERCP pancreatitis, cholangitis, perforation, or bleeding. Provides excellent anatomical detail of biliary tree and can demonstrate APBJ. ERCP is reserved for therapeutic indications (stenting, sphincterotomy for Type III) or tissue sampling (brush cytology).

3. A neonate presents with conjugated jaundice. USG shows a contracted gallbladder and a triangular cord sign at the porta hepatis. What is the most likely diagnosis, what confirmatory investigation would you arrange, and what pre-treatment enhances its sensitivity?

Your answer

Grade

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Most likely diagnosis: biliary atresia. Confirmatory investigation: HIDA scan (hepatobiliary iminodiacetic acid scan) — will show absence of isotope in the intestine, confirming failed biliary excretion. Pre-treatment: 5 days of phenobarbitone (liver enzyme inducer, increases biliary secretion to improve sensitivity). Gold standard confirmation: operative cholangiogram with liver biopsy at diagnostic laparoscopy.

4. What blood test findings would you expect in an uncomplicated biliary cyst versus one complicated by cholangitis?

Your answer

Grade

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Uncomplicated: liver tests often normal; may have mild cholestatic pattern (raised ALP, GGT) and conjugated hyperbilirubinaemia. CBC normal. Amylase normal. Complicated by cholangitis: leukocytosis with neutrophil predominance; raised CRP/ESR; cholestatic LFT pattern with raised bilirubin; raised amylase if concurrent pancreatitis; positive blood cultures; possible raised PT/INR from Vitamin K malabsorption.

5. Why does USG frequently miss Type III choledochal cysts, and what alternative imaging modality would you use?

Your answer

Grade

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Type III (choledochocele) is located in the intraduodenal/intramural portion of the distal CBD, deep in the retroperitoneum behind the duodenum. Bowel gas in the duodenum obscures this area on transabdominal USG. Alternative: EUS (endoscopic ultrasound) provides excellent visualisation of the intraduodenal distal CBD because the transducer is placed directly in the duodenum, bypassing bowel gas. MRCP also visualises this area well.

References

^[1] Senior notes: felixlai.md (Biliary cysts — Diagnosis and Radiological tests sections) ^[2] Senior notes: maxim.md (Choledochal cyst — Investigations section) ^[4] Senior notes: maxim.md (Recurrent pyogenic cholangitis section) ^[5] Senior notes: maxim.md (Cholangiocarcinoma — Investigations section); felixlai.md (Cholangiocarcinoma — Diagnosis section) ^[6] Senior notes: maxim.md (Hepatobiliary conditions — paediatric table: biliary atresia and choledochal cyst) ^[9] Senior notes: maxim.md (Choledocholithiasis section) ^[10] Senior notes: maxim.md (Biliary colic — USG findings section) ^[15] Senior notes: felixlai.md (Malignant biliary obstruction — Biochemical tests section; Gallbladder cancer — Tumour markers section) ^[16] Senior notes: maxim.md (Acute cholangitis section) ^[17] Senior notes: maxim.md (HBP investigations section)

Management of Biliary Cysts

Guiding Principles — Why We Treat

Before diving into the specifics, understand the fundamental logic behind treating biliary cysts:

1. Biliary cysts are pre-malignant. The lifetime risk of cholangiocarcinoma is 10–30% and increases with age. This is the single most compelling reason for definitive surgery ^[1].
2. Conservative observation is NOT acceptable for most types. Unlike simple hepatic cysts (which can be watched), biliary cysts have ongoing exposure to pancreatic juice reflux (via APBJ) that causes progressive epithelial damage and malignant transformation.
3. Internal drainage procedures (cyst-enterostomy) are obsolete. Older operations that simply drained the cyst into the bowel (without excising it) left the diseased epithelium in situ — the malignancy risk persisted or even increased. Modern management demands complete excision of the cyst ^[2].
4. The gallbladder must also be removed. Because APBJ affects the entire biliary epithelium including the gallbladder, and the gallbladder is in the surgical field. Prophylactic cholecystectomy is indicated in patients with APBJ but no biliary cysts because of the increased risk of gallbladder cancer ^[1].

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Management Algorithm

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Treatment by Todani Type — Detailed Breakdown

Type I: Complete Surgical Excision + Roux-en-Y Hepaticojejunostomy

This is the most common type and the paradigm for biliary cyst surgery. Understanding this operation well means you understand all the others.

What is done:

Type I = Complete surgical excision + Roux-en-Y hepaticojejunostomy ^[1]

1. Complete excision of the cyst: The entire dilated extrahepatic bile duct (cyst) is removed, from the hepatic duct confluence above down to the intrapancreatic CBD below. The cystic epithelium — which harbours the pre-malignant potential — is completely eliminated.
2. Cholecystectomy: The gallbladder is removed because (a) the cystic duct inserts into or near the cyst, and (b) APBJ exposes gallbladder epithelium to pancreatic juice → increased gallbladder cancer risk.
3. Roux-en-Y Hepaticojejunostomy (HJ): A loop of jejunum is divided, the distal limb (the "Roux limb") is brought up to the hepatic duct stump and anastomosed end-to-side. The proximal limb is reconnected to the jejunum further downstream (jejunojejunostomy), creating the characteristic "Y" shape.

Why Roux-en-Y?

Let me break down the name:

• Roux = César Roux, Swiss surgeon who devised this technique.
• en-Y = "in [the shape of] Y" (French).
• Hepatico- = hepatic duct; -jejunostomy = surgical connection to jejunum.

The Roux-en-Y configuration is chosen over simpler options (like choledochoduodenostomy) because:

Why not just drain the cyst into the duodenum (internal drainage)?

Historically, cyst-enterostomy (e.g., cystoduodenostomy or cystojejunostomy) was performed — creating a window between the cyst and bowel without removing the cyst. This is now obsolete because:

• The cyst epithelium remains in situ → ongoing malignancy risk (actually increased risk due to intestinal reflux into the cyst).
• Biliary stasis within the residual cyst → stone formation → recurrent cholangitis.
• Studies showed cholangiocarcinoma rates of up to 30% in patients with undrained/internally drained cysts.

Due to significant risk of malignancy and cyst excision can reduce complications such as recurrent cholangitis, cystolithiasis, choledocholithiasis and pancreatitis ^[1]

Long-term complications of Roux-en-Y HJ:

Most frequent long-term complication of Roux-en-Y hepatojejunostomy is stenosis of biliary-enteric anastomosis leading to jaundice, cirrhosis or cholangitis ^[1]

This occurs because:

• Any surgical anastomosis heals by scar tissue formation.
• The biliary-enteric junction is particularly prone to cicatricial (scar) narrowing because: (a) small calibre of the hepatic duct; (b) bile is a relatively corrosive fluid; (c) ischaemia at the suture line.
• Stricture → bile stasis → recurrent cholangitis → secondary biliary cirrhosis.
• Prevention: Meticulous surgical technique with tension-free, well-vascularised, mucosa-to-mucosa anastomosis.

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Type II: Simple Excision

Type II = Simple excision of cysts ^[1]

• Type II cysts are diverticula — true outpouchings (side pockets) from the CBD wall.
• The diverticulum is excised and the defect in the CBD wall is closed primarily (sutured).
• Extensive resection reserved for cysts with complicated presentations including jaundice or malignancy in the cyst ^[1].
• Because these are rare (2–3% of biliary cysts), the malignancy risk is lower, and a simple excision is usually sufficient.

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Type III: Endoscopic Management

Type III = Endoscopic sphincterotomy ^[1]

This is the exception to the rule of surgical excision. Why?

• Type III = choledochocele = cystic dilatation of the intraduodenal (intramural) portion of the distal CBD.
• The cyst protrudes into the duodenal lumen.
• It has the lowest malignancy risk of all Todani types.
• Surgical excision would require duodenotomy and potentially damage the pancreatic duct, which shares the common ampulla.

Procedure:

• Endoscopic snare resection can be performed for Type IIIA cyst (cyst lined by biliary epithelium) ^[1].
• Surgical or endoscopic resection can be performed for Type IIIB cyst (cyst lined by duodenal epithelium) ^[1].
• Endoscopic sphincterotomy effectively "unroofs" the cyst, allowing free drainage of bile into the duodenum and decompressing the choledochocele.

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Type IV: Complete Excision ± Partial Hepatectomy + Roux-en-Y HJ

Type IV = Complete surgical excision + Roux-en-Y hepatojejunostomy ^[1]

Type IV is subdivided into IVa (intra- + extrahepatic) and IVb (multiple extrahepatic only):

Type IVa (more common, more complex):

• Patients with intrahepatic cysts (Type IVA) require partial hepatectomy for excision of cyst and reconstruction with wide hilar Roux-en-Y hepatojejunostomy ^[1].
• The extrahepatic cyst is excised just as in Type I.
• For intrahepatic cysts: if confined to one lobe (usually left), a formal hepatectomy (left hepatectomy most commonly) is performed to excise the intrahepatic cystic disease entirely.
• If intrahepatic disease is bilateral but resectable, staged procedures or extensive hepatectomy with portal vein embolisation (to grow the future liver remnant) may be required.
• A wide hilar anastomosis is created to drain all remaining intrahepatic ducts into the Roux limb.

Type IVb (multiple extrahepatic only):

• Managed as for Type I — complete excision of all extrahepatic cysts + Roux-en-Y HJ.

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Type V (Caroli Disease): Supportive ± Hepatectomy ± Liver Transplantation

Type V = Supportive + Liver transplantation ^[1]

This is the most difficult type to manage because the cystic disease is purely intrahepatic and often diffuse:

Unilateral disease (confined to one lobe):

• Caroli disease can be treated with hemihepatectomy when it is confined to one side of the lobe ^[1].
• Left lobe involvement is more common → left hepatectomy.
• Curative if all diseased liver is removed.

Bilateral / diffuse disease:

• Treatment is largely supportive and is aimed at dealing with problems such as recurrent cholangitis and sepsis ^[1].
• Supportive measures include:
  • Antibiotics for episodes of cholangitis.
  • Ursodeoxycholic acid (UDCA) to improve bile flow and reduce stone formation.
  • ERCP/PTBD for stone clearance and drainage of infected segments.
• Patients with bilateral disease may eventually need a liver transplantation ^[1].
• Liver transplantation is the definitive cure for diffuse Caroli disease/syndrome, especially if complicated by:
  • Recurrent intractable cholangitis.
  • Secondary biliary cirrhosis with portal hypertension.
  • Associated congenital hepatic fibrosis (Caroli syndrome).
  • Suspicion of cholangiocarcinoma (if still within transplant criteria).

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Summary Table: Management by Todani Type

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Management of Acute Complications (Before Definitive Surgery)

Definitive surgery should never be performed in the setting of active sepsis/cholangitis. The acute complication must be managed first.

Acute Cholangitis Complicating a Biliary Cyst

The approach follows the same "RAD" framework used for any acute cholangitis ^[16]:

Management of cholangitis: Resuscitation → Antibiotics → Drainage ^[18][19]

Biliary Drainage Options for Acute Cholangitis:

QMH practice: ERCP → PTBD → ECBD ^[3]

Acute Pancreatitis Complicating a Biliary Cyst

• Supportive management: NPO, IV fluids, analgesia, monitor for organ failure.
• ERCP only if there is concurrent cholangitis or persistent biliary obstruction.
• Definitive cyst excision deferred until pancreatitis resolves.

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Special Scenarios

APBJ Without Biliary Cyst

Prophylactic cholecystectomy is indicated in patients with APBJ but no biliary cysts because of the increased risk of gallbladder cancer ^[1].

Why? Because APBJ allows pancreatic juice reflux into the gallbladder even when the bile duct itself is not cystically dilated. This chronic chemical insult to the gallbladder epithelium increases gallbladder cancer risk. Cholecystectomy removes the at-risk organ.

Malignancy Discovered Intra-operatively

• Intra-operative frozen section should be performed on the cyst wall and any suspicious areas during excision ^[5].
• If cholangiocarcinoma is confirmed:
  • The operation is converted to an oncological resection: extended hepatectomy, bile duct resection, portal lymph node dissection, and reconstruction with Roux-en-Y HJ.
  • Adjuvant chemotherapy may be considered post-operatively.

Incidentally Discovered Biliary Cyst (Asymptomatic)

• Even if asymptomatic, surgical excision is recommended for all types except Type III (which can be observed if small and asymptomatic).
• The malignancy risk is age-dependent and cumulative — waiting only increases the risk.
• The only exception is the patient who is unfit for surgery (advanced age, severe comorbidities), in whom the risks of surgery outweigh the benefits.

Biliary Cyst in Pregnancy

• Surgery is ideally deferred to the second trimester (if symptomatic) or post-partum.
• If cholangitis develops during pregnancy, drainage (ERCP or PTBD under radiation-minimised technique) and antibiotics should be instituted first.

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Roux-en-Y Hepaticojejunostomy — Understanding the Reconstruction

Since this is the reconstruction used in the majority of biliary cyst surgeries, let me detail it further:

Key surgical points:

• The Roux limb must be long enough (≥ 40 cm) to prevent reflux of enteric content to the biliary anastomosis.
• The anastomosis should be tension-free and well-vascularised (checking for pink, bleeding mucosa at the anastomotic edge).
• Mucosa-to-mucosa suturing technique is essential for optimal healing and patency.
• A wide hilar anastomosis is critical when reconstructing Type IVa cysts — all residual intrahepatic ducts must drain into the Roux limb.

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Post-operative Management and Long-term Surveillance

After definitive surgery, patients require lifelong surveillance because:

1. Anastomotic stricture — the most common long-term complication ^[1].
2. Residual intrahepatic disease — particularly in Type IVa where complete intrahepatic excision may not be possible.
3. Cholangiocarcinoma risk persists (albeit reduced) — malignancy can arise in any residual biliary epithelium, including the bile duct stump at the anastomosis.

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Contraindications and Considerations

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Paediatric-Specific Management

Complete excision of cyst and GB; Reconstruction with Roux-en-Y hepaticojejunostomy ^[6]

• In neonates, the key differential is biliary atresia. Once choledochal cyst is confirmed (operative cholangiogram), proceed to excision + reconstruction.
• Surgery can be performed safely in infants. Minimally invasive (laparoscopic or robotic) approaches are increasingly used in paediatric centres.
• Post-operative: long-term follow-up for anastomotic stricture and growth/nutritional monitoring.

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Active Recall - Management of Biliary Cysts

1. Describe the definitive surgical management of a Type I biliary cyst. Why is internal drainage (cyst-enterostomy) no longer performed?

Your answer

Grade

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Complete surgical excision of the entire extrahepatic cyst + cholecystectomy + Roux-en-Y hepaticojejunostomy. Internal drainage (cyst-enterostomy) is obsolete because it leaves the pre-malignant cyst epithelium in situ, maintaining or increasing cholangiocarcinoma risk (up to 30%). Excision removes the at-risk epithelium. Roux-en-Y reconstruction provides biliary drainage, prevents bile reflux (long Roux limb ≥ 40 cm), reduces stricture risk, and reduces recurrent cholangitis.

2. Which Todani type is managed endoscopically rather than surgically, and why?

Your answer

Grade

Show mark scheme

Type III (choledochocele). Managed with endoscopic sphincterotomy with or without snare resection. Reasons: (1) lowest malignancy risk of all types; (2) located in the intraduodenal segment, accessible endoscopically; (3) surgical excision would risk injury to the pancreatic duct sharing the ampulla. Type IIIA can be snare-resected, Type IIIB can be managed endoscopically or surgically.

3. A patient with a Type IVa biliary cyst has intrahepatic cysts confined to the left lobe with extrahepatic cyst involvement. What operation would you perform?

Your answer

Grade

Show mark scheme

Complete excision of the extrahepatic cyst + left hepatectomy (to excise the intrahepatic cysts) + cholecystectomy + wide hilar Roux-en-Y hepaticojejunostomy. The wide hilar anastomosis ensures all residual right intrahepatic ducts drain into the Roux limb. Intra-operative frozen section should be sent to rule out malignancy.

4. What is the most common long-term complication following Roux-en-Y hepaticojejunostomy for biliary cyst excision, and what clinical features would suggest it?

Your answer

Grade

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Anastomotic stricture of the biliary-enteric anastomosis. Leads to jaundice (rising bilirubin), cholestatic LFTs (rising ALP/GGT), recurrent cholangitis (fever, RUQ pain), and eventually secondary biliary cirrhosis if untreated. Caused by scar tissue formation at the anastomotic site. Detected by rising LFTs, USG showing proximal duct dilatation, confirmed by MRCP.

5. A patient with bilateral diffuse Caroli disease presents with recurrent cholangitis refractory to antibiotic and endoscopic treatment. What is the definitive management?

Your answer

Grade

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Liver transplantation. Rationale: bilateral diffuse disease cannot be excised by hepatectomy alone because insufficient liver remnant would remain. Supportive management (antibiotics, ERCP/PTBD for stone clearance, ursodeoxycholic acid) is used as a bridge. Liver transplantation cures the biliary disease and any associated congenital hepatic fibrosis. Hemihepatectomy is only appropriate for unilateral Caroli disease.

6. Why is prophylactic cholecystectomy indicated in patients with APBJ but no biliary cyst?

Your answer

Grade

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APBJ creates a long common channel outside the Sphincter of Oddi control, allowing pancreatic juice to reflux into the entire biliary tree including the gallbladder. Chronic exposure of gallbladder epithelium to activated pancreatic enzymes causes inflammation, metaplasia, dysplasia, and increased risk of gallbladder cancer. Removing the gallbladder eliminates the at-risk organ. This is recommended even in the absence of overt cystic dilatation.

References

^[1] Senior notes: felixlai.md (Biliary cysts — Treatment section) ^[2] Senior notes: maxim.md (Choledochal cyst — Management section) ^[3] Senior notes: felixlai.md (Acute cholangitis — Treatment section: QMH practice) ^[4] Senior notes: maxim.md (Recurrent pyogenic cholangitis section) ^[5] Senior notes: maxim.md (Gallbladder carcinoma — Treatment section; Cholangiocarcinoma — Management section) ^[6] Senior notes: maxim.md (Hepatobiliary conditions — paediatric table: choledochal cyst) ^[15] Senior notes: felixlai.md (Malignant biliary obstruction — Tumour markers section) ^[16] Senior notes: maxim.md (Acute cholangitis — Acute management RAD section) ^[18] Lecture slides: Malignant biliary obstruction.pdf (p15, p17) ^[19] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (p14) ^[20] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (p15) ^[21] Senior notes: felixlai.md (Percutaneous transhepatic biliary drainage section)

Complications of Biliary Cysts

Complications of biliary cysts can be divided into two broad categories:

1. Complications of the disease itself (i.e., the untreated or partially treated biliary cyst).
2. Complications of surgical treatment (i.e., post-operative complications of cyst excision and Roux-en-Y reconstruction).

Understanding the complications from first principles means tracing each one back to the core pathophysiology we have already established: biliary stasis, APBJ with pancreatic reflux, chronic epithelial inflammation, and the anatomical mass effect of the cyst.

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A. Complications of the Disease (Untreated Biliary Cyst)

These are the complications listed in the source notes ^[1][22]:

Complications of biliary cysts ^[1]:

• Cholangiocarcinoma
• Acute cholangitis
• Acute and chronic pancreatitis
• Stone formation (cystolithiasis, hepatolithiasis, cholelithiasis, choledocholithiasis)
• Intraperitoneal cyst rupture
• Secondary biliary cirrhosis
• Bleeding
• Gastric outlet or duodenal obstruction

Let me now explain each one in detail with its pathophysiological basis.

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1. Cholangiocarcinoma — The Most Important Complication

Cholangiocarcinoma (CC) ^[1][2] — this is the single most feared and most important complication of biliary cysts. It is the reason we operate on biliary cysts even when they are asymptomatic.

Pathophysiology:

The malignant transformation follows a metaplasia → dysplasia → carcinoma sequence:

1. APBJ allows chronic reflux of activated pancreatic enzymes (trypsin, phospholipase A₂, elastase) into the biliary tree.
2. These enzymes cause continuous chemical injury to the biliary epithelium lining the cyst.
3. The epithelium responds with hyperproliferation (attempting to repair the damage) and undergoes intestinal metaplasia (the biliary epithelium transforms to resemble intestinal epithelium — a more robust mucosa to "defend" itself).
4. Over time, genetic mutations accumulate in the rapidly dividing cells (p53 loss, K-ras mutations, CDKN2A inactivation).
5. Metaplastic epithelium progresses through low-grade dysplasia → high-grade dysplasia → invasive adenocarcinoma.

Key clinical points:

Red flags for malignant transformation in a known biliary cyst:

• New-onset or worsening painless jaundice
• Rapid weight loss
• Rising or markedly elevated CA 19-9
• Mural nodularity or solid component within the cyst on imaging
• New liver lesion(s) suspicious for metastasis

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2. Acute Cholangitis

Acute cholangitis ^[1]

Pathophysiology:

• Cystic dilatation creates a sump where bile pools and stagnates (poor "flushing" mechanism).
• Stagnant bile is an excellent culture medium for bacteria, particularly Gram-negative bacilli (E. coli, Klebsiella) which reach the biliary tree via:
  • Ascending infection from the duodenum (especially if APBJ bypasses the sphincter of Oddi barrier).
  • Haematogenous spread from portal venous blood.
• Obstruction (from the cyst itself, or from stones formed within the cyst) prevents drainage of infected bile.
• Result: Charcot's triad (fever, RUQ pain, jaundice) → if severe, Reynolds pentad (+ shock + confusion) — suppurative cholangitis with bacteraemia.

Clinical significance:

• Cholangitis is the most common acute presentation that brings adults with biliary cysts to medical attention.
• Recurrent cholangitis causes cumulative biliary epithelial damage, accelerating the metaplasia–dysplasia–carcinoma sequence.
• Management: RAD (Resuscitation, Antibiotics, Drainage) before definitive surgery ^[16].

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3. Acute and Chronic Pancreatitis

Acute and chronic pancreatitis ^[1]

Pathophysiology:

• APBJ creates a long common channel that allows bidirectional reflux — not only can pancreatic juice flow into the biliary tree, but bile can also reflux into the pancreatic duct.
• Bile reflux into the pancreatic duct activates pancreatic proenzymes (trypsinogen → trypsin) within the pancreas, triggering autodigestion → acute pancreatitis.
• Passage of stones from the cyst through the common channel can also cause transient obstruction of the pancreatic duct orifice → pancreatitis (analogous to gallstone pancreatitis).
• Repeated episodes of acute pancreatitis can lead to chronic pancreatitis with fibrosis, duct stricturing, exocrine/endocrine insufficiency.

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4. Stone Formation

Stone formation ^[1]:

• Cystolithiasis (stones and sludge forming within the cyst itself)
• Hepatolithiasis (intrahepatic stone formation)
• Cholelithiasis (gallstones)
• Choledocholithiasis (CBD stones)

Pathophysiology:

• Biliary stasis within the dilated cyst allows precipitation of bile components — calcium bilirubinate, cholesterol, and bile salts crystallise out of supersaturated, stagnant bile.
• Bacterial infection (particularly E. coli, Klebsiella) produces bacterial β-glucuronidase, which deconjugates bilirubin glucuronide → unconjugated bilirubin → combines with calcium → calcium bilirubinate (brown pigment) stones ^[4].
• This is exactly the same mechanism as in recurrent pyogenic cholangitis (RPC) ^[4].
• Stones cause further obstruction → more stasis → more stone formation → a vicious cycle.

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5. Intraperitoneal Cyst Rupture

Intraperitoneal cyst rupture ^[1]

Pathophysiology:

• The cyst wall is inherently abnormal — thinned, weakened, and damaged by chronic inflammation and pancreatic enzyme exposure.
• In neonates and infants, the cyst wall is particularly fragile.
• Elevated intracystic pressure (from obstruction, infection, or simply progressive dilatation) can cause the cyst to rupture into the peritoneal cavity.
• Bile spillage into the peritoneal cavity causes bile peritonitis — a chemical peritonitis caused by the cytotoxic and pro-inflammatory effects of bile salts and bilirubin on the peritoneal mesothelium.
• If infected bile leaks, this becomes secondary bacterial peritonitis — a surgical emergency.

Clinical features of cyst rupture:

• Sudden onset of severe diffuse abdominal pain.
• Signs of peritonitis: guarding, rigidity, rebound tenderness.
• Haemodynamic instability if significant.
• Abdominal free fluid on USG/CT.
• Emergency laparotomy is required.

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6. Secondary Biliary Cirrhosis

Secondary biliary cirrhosis (due to prolonged biliary obstruction and recurrent cholangitis) ^[1]

Pathophysiology:

• Chronic, sustained biliary obstruction (from the cyst itself or from complications such as stones and strictures) causes cholestasis.
• Cholestasis → retention of bile acids within hepatocytes → hepatocyte injury (bile acid toxicity).
• Concurrent recurrent cholangitis causes periductal inflammation and fibrosis around intrahepatic bile ducts.
• Over months to years, progressive fibrosis bridges portal tracts → cirrhosis (secondary biliary cirrhosis).
• Cirrhosis leads to portal hypertension → splenomegaly, ascites, variceal bleeding, hepatorenal syndrome.
• In Caroli syndrome (Type V), congenital hepatic fibrosis compounds this — patients may develop portal hypertension even before secondary biliary cirrhosis develops.

This is exactly the same mechanism seen in any cause of chronic biliary obstruction (e.g., PSC, strictures, malignant obstruction).

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7. Bleeding

Bleeding (due to erosion of the cyst into adjacent vessels or due to portal hypertension) ^[1]

Two mechanisms:

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8. Gastric Outlet or Duodenal Obstruction

Gastric outlet or duodenal obstruction (due to obstruction of duodenal lumen) ^[1]

Pathophysiology:

• A large extrahepatic cyst (especially Type I or Type III) can exert external compression on the adjacent duodenum (D1/D2).
• In Type III (choledochocele), the cyst protrudes into the duodenal lumen itself, directly causing intraluminal obstruction.
• Presents with: nausea, vomiting (especially post-prandial), early satiety, gastric distension.
• In severe cases, complete gastric outlet obstruction requiring nasogastric decompression and urgent surgery.

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B. Post-operative Complications (After Cyst Excision + Roux-en-Y HJ)

Even after successful surgery, patients are at risk for specific complications. These are divided into early and late categories:

Early Post-operative Complications

Late Post-operative Complications

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C. Complications Specific to Caroli Disease (Type V)

Caroli disease deserves special mention because its complications are more severe and complex than other types:

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D. Complications of ERCP (Relevant When Used for Drainage or Type III Management)

Since ERCP is used for drainage of acute cholangitis complicating biliary cysts and for treating Type III cysts, its complications are relevant ^[19][20]:

Potential complications of ERCP: perforation, bleeding from papillotomy, pancreatitis ^[20]

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Summary: Classification of Complications

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Active Recall - Complications of Biliary Cysts

1. List the eight major complications of untreated biliary cysts and identify the single most important one.

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Cholangiocarcinoma (most important, 10-30% lifetime risk), acute cholangitis, acute and chronic pancreatitis, stone formation (cystolithiasis, hepatolithiasis, cholelithiasis, choledocholithiasis), intraperitoneal cyst rupture, secondary biliary cirrhosis, bleeding (vessel erosion or portal hypertension), gastric outlet/duodenal obstruction.

2. Explain the pathophysiology of cholangiocarcinoma development in biliary cysts, starting from the APBJ.

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APBJ creates long common channel outside sphincter of Oddi control → chronic reflux of activated pancreatic enzymes (trypsin, phospholipase A2, elastase) into biliary tree → continuous chemical injury to biliary epithelium → hyperproliferation and intestinal metaplasia → accumulation of genetic mutations (p53, K-ras, CDKN2A) → low-grade dysplasia → high-grade dysplasia → invasive adenocarcinoma (metaplasia-dysplasia-carcinoma sequence). Risk highest in Types I and IVa, increases with age.

3. What is the most frequent long-term complication after Roux-en-Y hepaticojejunostomy for biliary cyst excision? Explain why it occurs and how it presents.

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Anastomotic stricture. Occurs because: scar tissue formation at the biliary-enteric junction is promoted by small calibre of the hepatic duct, bile exposure (corrosive), and ischaemia at suture line. Presents with progressive jaundice, cholestatic LFTs (rising ALP/GGT/bilirubin), recurrent cholangitis. If untreated leads to secondary biliary cirrhosis. Management: percutaneous balloon dilatation or revision hepaticojejunostomy.

4. How does stone formation in biliary cysts relate mechanistically to recurrent pyogenic cholangitis?

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Identical mechanism: biliary stasis within the dilated cyst allows bacterial colonization (E. coli, Klebsiella). Bacteria produce beta-glucuronidase which deconjugates bilirubin glucuronide into unconjugated bilirubin. Unconjugated bilirubin complexes with calcium to form calcium bilirubinate (brown pigment) stones. These stones cause further obstruction, more stasis, more infection, and more stone formation — a vicious cycle. Same pathophysiology as RPC.

5. A neonate with a known choledochal cyst presents with sudden diffuse abdominal pain, abdominal distension, and haemodynamic instability. What complication has likely occurred and what is the mechanism?

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Intraperitoneal cyst rupture causing bile peritonitis. Mechanism: the cyst wall is inherently thinned and weakened by chronic inflammation and pancreatic enzyme exposure; neonatal cyst walls are particularly fragile. Elevated intracystic pressure from obstruction/infection causes rupture into the peritoneal cavity. Bile salts and bilirubin cause chemical peritonitis (cytotoxic to peritoneal mesothelium). If bile is infected, secondary bacterial peritonitis ensues. Management: emergency laparotomy, peritoneal lavage, and definitive cyst excision with reconstruction.

References

^[1] Senior notes: felixlai.md (Biliary cysts — Complications section) ^[2] Senior notes: maxim.md (Choledochal cyst — Complications section) ^[4] Senior notes: maxim.md (Recurrent pyogenic cholangitis — Pathophysiology section) ^[5] Senior notes: felixlai.md (Cholangiocarcinoma — Pathogenesis section) ^[16] Senior notes: maxim.md (Acute cholangitis — Acute management RAD section) ^[19] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (p14) ^[20] Lecture slides: GC 200. RUQ pain, jaundice and fever Cholecytitis and cholangitis Imaging of GI system.pdf (p15) ^[22] Senior notes: felixlai.md (RPC — Complications section) ^[23] Senior notes: maxim.md (Cholecystectomy — Specific complications section) ^[24] Senior notes: felixlai.md (ERCP — Complications section)