Fig. 5.

Reproduced with permission from reference 12 (Santiago I, Loureiro R, Curvo-Semedo L, Marques C, Tardáguila F, Matos C, et al. Congenital cystic lesions of the biliary tree. American Journal of Roentgenoly. 2012;198(4):825-35.) The line diagrams depict the Todani modification of the Alonso-Lej classification and relative percentage of occurrence of each type of choledochal cyst. Type IA, is characterised by a cystic dilatation of the entire extra-hepatic bile duct. Type IB, is typically a focal segmental dilatation of the extra-hepatic bile duct, which is usually located distal to the cystic duct insertion. Type IC, comprises an abnormality comprising a smooth fusiform dilatation of the entire extra-hepatic bile duct. Type II, is a discrete diverticulum of the extra-hepatic bile duct, while Type III, is a dilatation of the intra-duodenal segment of the distal common bile duct. Type IVA, comprises of multiple sites of dilatation of both extra-hepatic and intra-hepatic biliary radicals, while Type IVB, manifests as multiple sites of dilatation only of the extra-hepatic bile duct. Type V, is recognised by multiple sites of saccular or cystic dilatation of only the intra-hepatic biliary tree (synonym: Caroli's disease, or communicating cavernous ectasia)