Mucosal changes of the gallbladder in anomalous union with the pancreatico-biliary duct system.

Histological examination of the gallbladder mucosa was made on a total of 39 patients with anomalous union of the pancreatico-biliary duct system. The most characteristic finding was mucosal hyperplasia of the gallbladder. Measurement of the height of the mucosa revealed that 15 cases (38.5%) showed mucosal hyperplasia composed of ordinary gallbladder epithelium without any metaplastic changes, including two cases of primary mucosal hyperplasia of the gallbladder. The other finding was metaplastic changes which were observed in 26 cases in various degrees, of whom 16 cases showed only focal metaplasia. These findings indicate that metaplasia frequently occurred in the gallbladder but the distribution of metaplasia was relatively focal in anomalous union with the pancreatico-biliary duct system. In our present materials there were nine cases of gallbladder adenocarcinoma and based on our classification, they were divided into seven cases of metaplastic type and two cases of non-metaplastic type. This ratio was not different from that of usual gallbladder carcinoma not complicated by this anomaly. These results indicate that the reflux of pancreatic juice into the gallbladder by anomalous union with the pancreatico-biliary duct system may cause two different effects on the gallbladder mucosa, the first being a proliferative effect resulting in mucosal hyperplasia and the other being chronic irritation causing metaplastic changes. The relation between these changes and the pathogenesis of gallbladder carcinoma is briefly discussed.