Todani classification of bile duct cysts

The Todani classification of bile duct cysts divides cysts of the bile duct into 5 groups:

Type 1 

Also known as a true choledochal cyst.

• account for 80 - 90% of all bile duct cysts
• characterized by fusiform dilation of the extrahepatic bile duct
  • Ia : dilatation of extrahepatic bile duct (entire)
  • Ib : dilatation of extrahepatic bile duct (focal segment)
  • Ic : dilatation of the common bile duct portion of extrahepatic bile duct

Theorized that choledochal cysts form as the result of reflux of pancreatic secretions into the bile duct via anomalous pancreaticobiliary junction.

Cyst should be resected completely to prevent associated complications (i.e. ascending cholangitis and malignant transformation).

Type 2 

Also known as a bile duct diverticulum.

• account for 3% of all bile duct cysts
• represent a true diverticulum

Saccular outpouchings arising from the supra-duodenal extrahepatic bile duct or the intra-hepatic bile ducts.

Type 3

Also known as a choledochocele.

• account for 5% of all bile duct cysts
• represent protrusion of a focally dilated, intramural segment of the distal common bile duct into the duodenum.

Choledochoceles may be successfully managed with endoscopic sphincterotomy, surgical excision, or both, in symptomatic patients.

Type 4

Multiple communicating intra- and extrahepatic duct cysts.

• second most common type of bile duct cysts (10%)
• subdivided into sub-types A and B
  • type 4b : fusiform dilation of the entire extrahepatic bile duct with extension of dilation of the intrahepatic bile ducts
  • type 4b : Multiple cystic dilations involving only the extrahepatic bile duct

Type 5

Also known as Caroli disease.

Caroli disease is a rare form of congenital biliary cystic disease manifested by cystic dilations of intrahepatic bile ducts.

Association with benign renal tubular ectasia and other forms of renal cystic disease.