Todani Classification of Choledochal cysts
Mnemonic: Consider I is “Extrahepatic” and V is “Intrahepatic”, then –
- Type I, II and III = Extrahepatic
- Type IV = Extrahepatic + Intrahepatic
- Type V = Intrahepatic
Most common: Type I
2nd most common: Type IV
Type I-III: Extrahepatic
Mnemonic: 123 EDC
Type I: Entire CBD dilated
Type II: Diverticulum
Type III: Choledochocele (Intraduodenal portion of CBD)
Type IV: Extrahepatic + Intrahepatic
Mnemonic: A for “And or Additional” and B for “Bunch”
Type IVa: Both intrahepatic AND extrahepatic cysts
Type IVb: Multiple extrahepatic cysts only
Type V: Intrahepatic cysts only (Caroli’s disease)

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Thank you. Interesting.