Pathologic features of hepatolithiasis in Japan.

A national survey of pathologic features of hepatolithiasis was conducted in Japan. The significance of hepatobiliary lesions in the pathogenesis of hepatolithiasis was evaluated in 31 autopsy livers and 242 surgically resected livers. Eighty-two percent shared several morphologic and clinical features, eg, the presence of multiple calcium bilirubinate or brown pigment stones within the intrahepatic duct and a characteristic hepatobiliary morphology. These cases were distributed throughout Japan without distinct geographic differences. The stones were found in the left and/or right hepatic duct and/or their tributaries. The ducts that contained stones had uneven dilatation of their lumena with focal stenosis. The walls of the involved ducts were thickened mainly by fibrosis. The hepatic parenchyma associated with stones within intrahepatic bile ducts showed mild to severe atrophy and fibrosis. Histologically, the ducts that contained stones showed fibrosis, proliferation of mucous and serous glands, and inflammatory cell infiltration in their walls and the periductal tissue. A large amount of mucus secreted from the affected ducts was seen within the biliary sludge and calcium bilirubinate stones were found in the involved ductal lumena. These findings suggest that the large amount of mucus and the formation of unevenly dilated ductal lumena may be important in the formation of intrahepatic calculi because these factors may favor nucleation and promote local bile stasis, thereby accentuating the ductal changes and stone formation (a vicious cycle).