From the Guidelines
Choledochal cysts are classified using the Todani classification system, which categorizes these congenital bile duct abnormalities into five main types based on their anatomical location and morphology. The Todani classification system is a widely accepted method for categorizing choledochal cysts, and it is essential for surgical planning and determining the extent of resection needed 1. The classification system includes:
- Type I cysts: saccular or fusiform dilatation of the common bile duct
- Type II cysts: true diverticula protruding from the common bile duct
- Type III cysts: limited to the intraduodenal portion of the common bile duct, also called choledochoceles
- Type IV cysts: multiple dilatations, subdivided into type IVA (affecting both intrahepatic and extrahepatic bile ducts) and type IVB (multiple extrahepatic bile duct cysts only)
- Type V cysts: multiple intrahepatic bile duct cysts, also known as Caroli disease, characterized by dilatation of intrahepatic bile ducts 1.
The diagnosis of choledochal cysts, particularly Caroli disease, can be confirmed using magnetic resonance cholangiopancreaticography, which allows for optimal visualization of the biliary tree 1. The management of choledochal cysts, including surgical excision, is crucial to prevent malignant transformation, with cholangiocarcinoma developing in approximately 10-30% of untreated patients over time 1. Surgical excision of the cyst with biliary-enteric reconstruction is recommended, especially in patients with choledochal cysts associated with an anomalous pancreaticobiliary junction, and should be performed by a team with hepatobiliary surgery expertise 1.
From the Research
Choledochal Cyst Classification
- The Todani classification is the most commonly used system to classify choledochal cysts, which are rare cystic dilatations of the intrahepatic and/or extrahepatic bile ducts 2, 3, 4, 5.
- According to the Todani classification, choledochal cysts are categorized into different types based on their anatomical characteristics, including:
- Type I: The most common type, characterized by a dilatation of the extrahepatic bile duct 2, 4.
- Type II: A diverticulum of the extrahepatic bile duct 5.
- Type III: Also known as a choledochocele, characterized by a dilatation of the intraduodenal portion of the common bile duct 3.
- Type IV: Characterized by multiple dilatations of the intrahepatic and/or extrahepatic bile ducts 2, 4.
- Type V: Also known as Caroli's disease, characterized by multiple dilatations of the intrahepatic bile ducts 6.
- The Todani classification is widely used in clinical practice due to its simplicity and reproducibility, allowing for comparative analysis between different series of patients 5.
- However, some clinicians have questioned the clinical significance and viability of the Todani classification, as it does not take into account factors such as epidemiology, pathogenesis, and risk of malignant transformation 5.
- Despite these limitations, the Todani classification remains the current standard for classifying choledochal cysts, and is used to guide management and treatment decisions 2, 3, 4.