According to Todani classification of bile duct cysts, there are FIVE major classes of bile duct cysts exist (ie, types I-V), with sub-classifications for types I and IV (ie, types IA, IB and IC; types IVA and IVB).
No strong unifying etiologic theory exists for bile duct cysts. The pathogenesis is probably multifactorial. In many patients with bile duct cysts, an anomalous junction between the common bile duct and the pancreatic duct can be demonstrated. This occurs when the pancreatic duct empties into the common bile duct more than 1 cm proximal to the ampulla.
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| Diagram showing the normal anatomy of the biliary and pancreatic ducts. |
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| Diagram showing the biliary tree. |
Type I
Also known as a true choledochal cyst. It is the most common type and represent 80-90% of bile duct cysts. They consist of saccular or fusiform dilatations of the common bile duct, which involve either a segment of the duct or the entire duct.
- Type IA is saccular in configuration and involves either the entire extrahepatic bile duct or the majority of it.
- Type IB is saccular and involves a limited segment of the bile duct.
- Type IC is more fusiform in configuration and involves most or all of the extrahepatic bile duct.
Type I Cyst should be resected completely to prevent associated complications (i.e. ascending cholangitis and malignant transformation).
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| Bile Duct Cyst Type I (True Choledochal Cyst). |
Type II
Also known as a bile duct diverticulum.It accounts for 3% of all bile duct cysts, appearing as an isolated diverticulum protruding from the wall of the common bile duct (Saccular outpouchings arising from the supra-duodenal extrahepatic bile duct or the intra-hepatic bile ducts). The cyst may be joined to the common bile duct by a narrow stalk.
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| Bile Duct Cyst Type II (Bile Duct Diverticulum). |
Type III
Also known as a choledochocele. It accounts for 5% of all bile duct cysts, arising from the intra-duodenal portion (distal end) of the common bile duct.
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| Bile Duct Cyst Type III (Chledochocele). |
Type IV
Multiple communicating intra- and extra-hepatic duct cysts. It is the second most common type of bile duct cysts (10%). It is subdivided into sub-types A and B
- Type IVA : fusiform dilation of the entire extrahepatic bile duct with extension of dilation of the intrahepatic bile ducts.
- Type IVB : Multiple cystic dilations involving only the extrahepatic bile duct.
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| Bile Duct Cyst Type IV. |
Type V
Also known as Caroli disease. Caroli disease is a rare form of congenital biliary cystic disease manifested by cystic dilations limited to intrahepatic bile ducts. It is associated with benign renal tubular ectasia and other forms of renal cystic disease.
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| Bile Duct Cyst Type V (Caroli Disease). |