The morphological and histopathological assessment of Alagille syndrome with extrahepatic bile duct obstruction: the importance of the differential diagnosis with subgroup “o” biliary atresia

Purpose: The differential diagnosis between Alagille syndrome (AGS) with extrahepatic bile duct obstruction (EHBDO) and biliary atresia (BA) is difficult. We report a case series of AGS with EHBDO with detailed validation of the morphological and histopathological features for the differential diagnosis of BA. Methods: Six liver transplantations (LTs) were performed for AGS with EHBDO. All patients were diagnosed with BA at the referring institution and the diagnosis of AGS was then confirmed based on a genetic analysis before LT. We verified the morphological and histopathological findings of the porta hepatis and liver at the diagnosis of BA and at LT. Results: All patients had acholic stool in the neonatal period and were diagnosed with BA by cholangiography. The gross liver findings included a smooth and soft surface, without any cirrhosis. The gross findings of the porta hepatis included aplasia of the proximal hepatic duct, or subgroup “o”, in five patients. The histopathological examination of the EHBD also revealed obstruction/absence of the hepatic duct. There were no patients with aplasia of the common bile duct. Conclusions: Aplasia of the hepatic duct and the macroscopic liver findings may help in to differentiate between AGS with EHBDO and BA.