biliary rule 4:Choledocal cyst

Todani Classification:
This classification classifies the choledochal cysts into 5 categories.
Type I is a true choledochal cyst with focal dilatation of the extra biliary duct.
This is the most frequent type (90-95% of the cases).
Type II is a diverticulum of the extra biliary duct and many believe that this entity is not related to an anomalous pancreatico-biliary junction.
Type III is a choledochocele, where there is dilatation of the distal part of the bile duct.
Type IV is also a true choledochal cyst with dilatation of the entire extra bile duct with involvement of portions of the intrahepatic bile ducts.
Type V,  is Caroli disease.
We now know, that Caroli is a different disease.


The intrahepatic ducts taper normally to the periphery, indicating that there is no obstruction.
Type II and III are extremely rare and it is debatable whether or not these are true choledochal cysts.