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Choledochal cysts are congenital cystic dilatations of the biliary tree, which may involve extrahepatic and/or intrahepatic bile ducts. They are associated with an abnormal pancreaticobiliary junction (PBJ), allowing reflux of pancreatic enzymes into the bile duct, leading to inflammation and dilatation.

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https://www.youtube.com/watch?v=WKK3g3BCOn0

Classification

Todani Classification with Alonso-Lej Modification:

Type Incidence Description
I 50–90% Fusiform or saccular dilatation of the extrahepatic bile duct (EBD)
• Ia: Cystic dilatation with associated APBJ
• Ib: Focal segmental dilatation (typically distal) without APBJ
• Ic: Diffuse fusiform dilatation of the EBD with associated APBJ, that can involve the intrahepatic ducts
II 2–3% True choledocal diverticulum
III 1–5% Choledochocele involving only the intraduodenal CBD
IV 30–40% Intra- and extrahepatic duct involvement
• IVa: Multiple fusiform or saccular dilation of the EBD and the intrahepatic bile ducts (usually associated with APBJ)
• IVb: Multiple cystic dilatations involving only the extrahepatic bile duct
V Caroli’s disease

![Illustrations show the Todani classification system for choledochal cysts. Type I cysts (the most common morphology) show dilatation of the extrahepatic bile duct. Type Ia cysts show cystic dilatation of the extrahepatic bile duct, with an abnormal pancreaticobiliary junction (not pictured). Type Ib cysts show focal dilatation of the common bile duct, without an abnormal pancreaticobiliary junction. Type Ic cysts show fusiform dilatation involving the common hepatic and common bile duct with an abnormal pancreaticobiliary junction. Type II cysts are diverticula of the supraduodenal extrahepatic duct, usually projecting to the right. Type III cysts (ie, choledochoceles) show cystic dilatation of the intramural segment of the distal common bile duct protruding into the duodenum. Type IV cysts consist of multiple foci of dilatation, often with an abnormal pancreaticobiliary junction and involving either intrahepatic and extrahepatic ducts (IVa) or extrahepatic ducts alone (IVb). Type V cysts (ie, Caroli disease) are characterized by multiple intrahepatic cysts, without extrahepatic abnormality.

Camila Lopes Vendrami, Thorson DL, Borhani AA, et al. Imaging of Biliary Tree Abnormalities. Radiographics. 2024;44(8). doi:https://doi.org/10.1148/rg.230174](attachment:c6605b59-d5e3-4ae1-ac30-02e1fef08bbf:images_large_rg.230174.fig1.jpg)

Illustrations show the Todani classification system for choledochal cysts. Type I cysts (the most common morphology) show dilatation of the extrahepatic bile duct. Type Ia cysts show cystic dilatation of the extrahepatic bile duct, with an abnormal pancreaticobiliary junction (not pictured). Type Ib cysts show focal dilatation of the common bile duct, without an abnormal pancreaticobiliary junction. Type Ic cysts show fusiform dilatation involving the common hepatic and common bile duct with an abnormal pancreaticobiliary junction. Type II cysts are diverticula of the supraduodenal extrahepatic duct, usually projecting to the right. Type III cysts (ie, choledochoceles) show cystic dilatation of the intramural segment of the distal common bile duct protruding into the duodenum. Type IV cysts consist of multiple foci of dilatation, often with an abnormal pancreaticobiliary junction and involving either intrahepatic and extrahepatic ducts (IVa) or extrahepatic ducts alone (IVb). Type V cysts (ie, Caroli disease) are characterized by multiple intrahepatic cysts, without extrahepatic abnormality.

Camila Lopes Vendrami, Thorson DL, Borhani AA, et al. Imaging of Biliary Tree Abnormalities. Radiographics. 2024;44(8). doi:https://doi.org/10.1148/rg.230174

Etiopathogenesis

Clinical Features

Classical triad (seen in <20%):

  1. Abdominal pain
  2. Jaundice
  3. Palpable mass

Other symptoms: