Morphometrical and immunohistochemical study of intrahepatic bile ducts in biliary atresia.

Background: Extrahepatic biliary atresia results from a progressive destruction of the bile ducts by an inflammatory fibrosing process which leads ultimately to cirrhosis of biliary type. The etiology of the disorder remains unknown. The histological features include cholestasis, ductular proliferation, eventual loss of intrahepatic bile ducts, and ducts with primitive embryonic shape (ductal plate malformation).

Purpose: To examine the morphological changes of the biliary intrahepatic ducts, we aimed at investigating the cell proliferation and the diameter of the interlobular bile ducts in extrahepatic biliary atresia, and in normal liver children.

Methods: Liver samples from 35 patients with biliary atresia and 10 from control normal children were used. Immunoexpression of cytokeratin 19 was evaluated and a double-staining procedure was performed with cytokeratin 8/proliferating cell nuclear antigen. The stereological measurements of the intrahepatic bile ducts diameter were evaluated by a computerized system of image analysis.

Results: The patterns of intrahepatic cholangiopathy in biliary atresia were obstructive features (42.86%), paucity of intrahepatic bile ducts (20%), ductal plate malformation (28.57%), and ductal plate malformation associated with paucity of intrahepatic bile ducts (8.57%). The average external diameter of interlobular bile ducts in biliary atresia was smaller than that of the control infant livers. Among the four patterns of biliary atresia cholangiopathies, those associated with ductopenia showed the smallest bile duct diameter. There was a negative correlation between the bile duct to portal space ratio and the age of the child at the time of Kasai portoenterostomy. Only in biliary atresia are the bile duct cells stained with proliferating cell nuclear antigen.

Conclusion: (i) In biliary atresia, both ductular metaplasia and ductular proliferation were observed; (ii) biliary atresia associated with ductopenia showed narrowing of interlobular ducts, probably as a consequence of degeneration with atrophy and fibrosis.