Nodular formations in the rat small intestine after local abdominal x-irradiation.

The abdomen of Wistar rats was irradiated locally with 1000 to 2000 rads. Approximately 2 months following irradiation, visible nodules were found in the intestines of the groups receiving irradiation. Nodule incidence was 80 to 100% in groups that received 1750 or 2000 rads, 50% in the 1500-rad groups, and 3% in the 1000-rad groups, respec tively. The histology of the nodules revealed adenomatous hyperplasia, including invasion of submucosa, muscle lay ers, and serosa of the small intestine accompanied by an area of fibrous tissue resulting from desmoplastic reaction by irradiation injury.