Choledochal cyst

Overview

Congenital cystic dilatation of intra/extrahepatic bile ducts.
Strong female and East Asian predominance; often presents in childhood, but many adults now picked up on imaging.

Summary

Think “abnormal cystic/fusiform ductal dilatation that communicates with the biliary tree + ↑ malignancy risk”.

Often associated with abnormal pancreatobiliary junction → pancreatic reflux into CBD → inflammation, weakness, dilatation.
Classic (but uncommon) triad: RUQ pain + jaundice + palpable mass.
Adults: recurrent cholangitis, pancreatitis, stones, or incidental on US/CT/MR.

US: cystic structure in porta hepatis continuous with CBD; look for intrahepatic duct (IHD) dilatation, stones, sludge.
CT/MR: well-defined fluid lesion following bile; exclude hepatic cyst/pseudocyst/duodenal diverticulum.
MRCP (exam favourite): best non-invasive anatomy + classification; shows communication with ducts and pancreaticobiliary junction.

Type I – Isolated extrahepatic duct dilatation (most common)
- IA: cystic; IB: segmental; IC: fusiform.
Type II – Saccular diverticulum of CBD.
Type III – Choledochocele (intraluminal cystic dilatation in duodenal wall).
Type IV
- IVa: multiple extrahepatic + intrahepatic cysts.
- IVb: multiple extrahepatic cysts only.
Type V – Caroli disease (intrahepatic only; “central dot sign”).
- With congenital hepatic fibrosis → Caroli syndrome.

Caution

Markedly ↑ risk of cholangiocarcinoma and gallbladder carcinoma, especially Types I, IV and V; risk persists after drainage-alone surgery.

Definitive treatment is complete cyst excision with biliary-enteric reconstruction
- Liver resection or transplant for advanced Caroli disease.
Key differentials for porta hepatis cystic lesion:
- pancreatic pseudocyst
- duodenal diverticulum
- hepatic cyst
- gallbladder duplication
  MRCP helps by showing ductal communication pattern.