Ultrastructural aspects of liver injury with special reference to small bile ducts in patients with ulcerative colitis.

Liver tissue specimens taken at colectomy from 29 patients with chronic ulcerative colitis were studied by electron microscope. The fine-structural alterations were correlated with light microscopy and with biochemical liver function tests. The purpose was to identify ultrastructural features which could explain the pathogenesis of sclerosing cholangitis. Severely injured bile-duct epithelial cells were seen in three out of the eight light-microscopically diagnosed cholangitis cases, in the two cases of non-specific reactive hepatitis, and in the two fatty livers. Four cholangitis cases had, in heavily thickened bile-duct basement membranes, translucent areas containing bile-like material. Bile-duct microvilli were often blunted, and reduced in number. Intracanalicular bile thrombi and bile inclusions in hepatocytes were seldom seen, mostly but not exclusively in cholangitis. The fine-structural alterations apparently represent various stages of liver injury. These findings do not appear to be specific, but their prominence seems to correlate with the progression of the disease, at least in the case of histological parameters, but also in serum enzyme activities indicative of cholestasis. The bile-like electron-dense material found in proliferating basement membranes, very possibly regurgitated into the injured bile-duct wall after epithelial injury, could enhance the development of periductal fibrosis, leading to progression of sclerosing cholangitis.