HISTOLOGICAL-EVALUATION OF THE INTRAHEPATIC BILIARY TREE IN INTRAHEPATIC CHOLESTEROL STONES, INCLUDING IMMUNOHISTOCHEMICAL STAINING AGAINST APOLIPOPROTEIN-A-I

Apolipoprotein A-1 is known to be one of inhibiting factors of cholesterol nucleation in bile, and decreased activity of apolipoprotein A-1 is considered to predispose cholesterol-supersaturated bile to formation of cholesterol crystals. To study the pathogenesis of the intrahepatic formation of cholesterol stones, we examined surgically resected liver specimens from six patients with intrahepatic cholesterol stones and compared the characteristic histopathological features with those of intrahepatic calcium bilirubinate stones, using morphological examination and immunohistochemical staining against apolipoprotein A-1. Morphologically, in all six patients with cholesterol stones the severity of chronic proliferative cholangitis with proliferation of the mucus-producing glandular elements in the walls of the large bile duct or periductal tissues was less extensive than that seen with calcium bilirubinate stones, and cholesterol crystals had formed in the septal and interlobular bile ducts. Immunohistochemically, unlike the normal liver and calcium bilirubinate stone-containing lobes, the hepatocytes and the epithelial lining of the bile ducts and peribiliary glands of the cholesterol stone-containing lobes did not react completely (some of the epithelial cells reacted only faintly) with apolipoprotein A-1 antibody. These findings suggest that an abundance of mucous substance and bacterial infection of the biliary tree may not be necessary for the formation of cholesterol stones, compared with findings in cases of calcium bilirubinate stones. We suggest that cholesterol crystals may be produced in the septal and interlobular bile ducts in the microenvironment of cholesterol-supersaturated bile and decreased activity of apolipoprotein A-1.