Pathogenesis of bleeding colonic diverticulosis: new concepts.

Diverticulosis of the colon is a common disease of the older population which develops in those people who eat highly refined carbohydrate diets free of roughage. High intraluminal pressures are created in the resultant narrowed colon which tends to push the mucosa between circular muscle bundles through oblique connective tissue clefts containing the vasa recta. Massive bleeding of the colon is most commonly due to right-sided diverticulosis. It can be explained by chronic injury to the vasa recta which lie within the submucosa of the diverticulum from the apex to the antimesenteric orifice. Rupture has been documented to occur when the wall of the artery facing the diverticulum becomes weakened by intimal fibrosis, elastic lamina fragmentation, and smooth muscle atrophy. This occurs at the dome and at the antimesenteric orifice of the diverticulum. Selective angiography is the diagnostic tool of choice. Recent advances in pharmacoagiography and and embolization promise successful treatment with lower morbidity than surgical resection.