Classification of congenital biliary cystic disease: special reference to type Ic and IVA cysts with primary ductal stricture.

Congenital biliary cysts occur not only in the choledochus but also everywhere in the biliary tree, and are frequently accompanied by pancreatobiliary malunion. Alonso-Lej and colleagues first classified choledochal cysts into three types, in 1959. Due to the recognition of intrahepatic involvement, we refined their classification into six types, in 1977, and this has become the reference. However, this classification does not include the concept of pancreatobiliary malunion and has caused some confusion, especially in regard to types Ic and IVA. Type Ic, showing fusiform dilatation, has a pancreatobiliary malunion and often extends continuously to the intrahepatic duct. Type IVA, with intrahepatic involvement, shows primary ductal stricture, especially around the hepatic hilum and umbilicus. The incidence of the stricture is considerably greater than was previously assumed, and upstream intrahepatic ducts often join the dilated duct, with distinct caliber change. Intrahepatic dilatation may develop primarily, due to the stricture, combined with weakness of the duct wall. This stricture can be corrected by portal dissection in the liver to obtain a large anastomosis. In patients with intrahepatic involvement, we should carefully find the stricture by suitable cholangiograms, or by intraoperative cholangioscopy. Detecting the ductal stricture is obviously important, rather than classifying the cyst as type Ic or IVA.