Duodenal reflux through the pylorus induces gastric adenocarcinoma in the rat

We investigated whether duodenal reflux through the pylorus is involved in the development of gastric cancer. Male Wistar rats weighing 230-250 g were subjected to three types of operative procedures: (i) allowing reflux through the pylorus; (ii) allowing reflux through a gastrojejunal stoma; and (iii) gastrotomy. No carcinogens were given, and the animals were killed 50 weeks after surgery. No cancers were detected in any of the 18 animals with gastrotomy. In contrast, seven (41%) of 17 animals with reflux through the pylorus and four (31%) of 13 animals with reflux through the stoma had adenocarcinoma. Differences in the incidence between both reflux groups and the gastrotomy group were significant (P < 0.01 and P < 0.05 respectively). All of the adenocarcinomas developed in the pyloric mucosa near the pylorus in the animals with reflux through the pylorus, and in the oxyntic mucosa near the stoma in those with reflux through the stoma. Adenocarcinomas appeared as a polyploid mass with or without slight central erosion. Most of the adenocarcinomas were of the well-differentiated tubular type, and the others were of the mucinous type. No differences in either the histologic type or depth of invasion of the adenocarcinoma were recognized between the two duodenogastric reflux groups. Precancerous or paracancerous lesions, such as adenoma, adenocystic proliferation, and stomal pseudopyloric metaplasia, were more frequently found in the same region as the adenocarcinomas. These findings suggest that duodenogastric reflux in the rat has potent carcinogenic activities not only in the oxyntic mucosa through the stoma, but also in the pyloric mucosa through the pylorus.