Kasai classification is used to describe the three main anatomical types of biliary atresia.
- type I: obliteration of common bile duct (patent cystic and common hepatic duct)
- IIa: obliteration of common hepatic duct (patent cystic and common bile duct), sometimes with a cyst at hilum hence termed cystic biliary atresia
- IIb: obliteration of common hepatic duct, cystic and common bile duct
- type III: obliteration of left and right main hepatic ducts at the level of porta hepatis (most common, 90%)
Note: some authors have mentioned this anatomical classification as Japanese and Anglo-Saxon classification 1.