Biliary Sludge and Microcalculi in Intrahepatic Bile Ducts

Abstract

To clarify the morphology and pathogenesis of intrahepatic calculi in the incipient stage, we examined biliary sludge and microcalculi in intrahepatic bile ducts by morphologic and X-ray microanalytical methods in 18 (1.5%) among 1,179 autopsied livers. The hepatobiliary conditions of these 18 livers were intra- and extrahepatic biliary obstruction in 14 cases, hepatic fibrosis in three cases, and cirrhosis with hepatocellular carcinoma in the remaining one. Grossly, brown-pigmented microcalculi were observed floating in biliary sludge. Microscopically, the biliary sludge was composed of mucin, fibrinous materials, desquamated epithelial cells and a few bilirubin granules. The microcalculi were embedded in the sludge and consisted of mucin and precipitates of bilirubin with a granular, lamellar or amorphous appearance. Bacterial colonies were recognized in both the sludge and microcalculi in all but three cases. Intrahepatic bile ducts harboring sludge and microcalculi showed a minimal to moderate degree of glandular proliferation with mucin production. X-ray microanalysis disclosed that the sludge contained little calcium ion, whereas microcalculi were calcium-rich. These findings suggest that biliary obstruction, bacterial infection and mucin hypersecretion play an important role in the formation of intrahepatic biliary sludge and microcalculi, and that sludge is causally related to the formation of intrahepatic microcalculi. Intrahepatic microcalculi and biliary sludge may represent a pathogenetic sequence in the early stage of calcium bilirubinate hepatolithiasis.