“…In this schema, patients with a type I cyst have an extrahepatic biliary dilatation that can be divided into three groups: (A) cystic dilatation of the entire common bile duct, (B) focal segmental dilatation of the common bile duct, and (C) fusiform dilatation of the extrahepatic biliary tree. In most series,1,2,3,4, this is the most common type of choledochal cyst, accounting for between 40% and 80% of all cases. A type II cyst is a true diverticulum of the common bile duct and is quite rare (<2%).…”