Polypoid prolapsing mucosal folds in diverticular disease.

Redundant or polypoid mucosal folds were found in eight surgically resected sigmoid colons with diverticular disease. Grossly, they were either swellings of mucosal folds or larger, leaflike, smooth-surfaced polyps with broad bases arising from mucosal folds. The number of lesions ranged from one to 11, and when multiple they formed two rows between diverticula. Swollen mucosal folds showed submucosal and mucosal vascular congestion, scanty thrombi, edema, hemorrhage, and hemosiderin deposition. Some were markedly inflamed. Polypoid lesions also showed crypt elongation and fission, upgrowth of muscle from the muscularis mucosae, and hyperplastic-metaplastic change typical of mucosal prolapse. One polyp showed evidence of an inverted diverticulum. Two cases displayed diffuse mucosal inflammation resembling inflammatory bowel disease in the region of the polyps. We speculate that these lesions result from a combination of venous congestion and mucosal redundancy secondary to spastic contraction of the muscle coat.