Ultrastructural study on hyperplastic epithelium of rat common bile duct after choledochoenterostomy.

Hyperplasia of the choledochal epithelium occurs in rats after choledochoenterostomy. It is tubular or papillary and not like small intestinal mucosa in rats with choledochojejunostomy. It is, however, like large intestinal mucosa in rats with choledochocolonostomy. We investigated the ultrastructure of the hyperplastic epithelium in the two experimental groups of rats in this study. The main constituent cells of the hyperplasia of both the groups were like the principal cells of the control, but differed in that they had long microvilli and contained an aggregation of mucus droplets and an increased number of lysosomes. These findings were not seen in the control. The microvilli were sparse in the choledochojejunostomy group, but were dense in the choledochocolonostomy group. These findings suggest that the main function of the epithelium may be cytoprotection in the choledochojejunostomy group and both resorption and cytoprotection in the choledochocolonostomy group.