Less common are bowel obstruction, fistulas, bowel perforation, and massive rectal bleeding. The initial signs and symptoms occur within 6 to 18 months following radiotherapy. Radiologic findings include submucosal thickening, single or multiple stenoses, adhesions, and sinus or fistula formation. 2 Microscopic findings include villi that are fibrotic, or may be lost altogether. Ulceration is common, varying from simple loss of epithelial layers to ulcers that may penetrate to different depths of the intestinal wall, even to the serosa.
Lymphatic tissue is often atrophic or absent.
The submucosa is severely diseased. Arterioles and small arteries show profound changes with hyalinization of the entire wall thickness. The muscularis is often distorted or focally replaced by fibrosis. The diagnosis of chronic radiation enteritis may be difficult to make. Clinically and radiologically recurrent tumor needs to be ruled out.