Cystic dilatation of the bile ducts: classify it (Todani I–V), show the anomalous pancreaticobiliary junction on MRCP, and look for stones, pancreatitis and — in adults — malignancy.
Orient first
- Type I (fusiform or cystic CBD) is commonest; type IV involves intra- and extrahepatic ducts; type V is Caroli disease (verify classification).
- A long common channel (anomalous pancreaticobiliary junction) causes reflux of pancreatic juice.
- Excision is recommended because of cholangiocarcinoma risk.
Acquire the study
- Curvilinear and linear probes; fasting.
The manoeuvre
- A cyst at the porta in continuity with the CBD in the longitudinal plane; its size in cm.
- Intrahepatic duct dilatation in mm (type IV or V).
- Sludge or stones in the cyst; gallbladder separate from the cyst.
What confirms it
- Cystic dilatation in continuity with the biliary tree on MRCP.
What licenses you to exclude it
- Normal duct calibre for age excludes a choledochal cyst.
The classic misread
- Calling a duodenal duplication or pancreatic pseudocyst a choledochal cyst — show continuity with the duct.