The colonoscope is slowly withdrawn during this screening colonoscopy down from the transverse colon, back around the splenic flexure, and down the descending colon, and reveals this finding a colonic diverticula. Diverticulosis is a common, acquired, age-related occurrence affecting over 50% of the western adult population over the age of 50. It is seen rarely in Africa and Asia where the dietary fiber content is traditionally higher. Thus most investigators feel that low fiber diets are related to the development of this condition. Ironically, colonic diverticula are not true diverticula but rather pseudodiverticula in that the sac includes layers of the mucosa and submucosa that push through rather than include the outer muscular layer. As with the small bowel the colon has an inner circular muscular layer, but the outer longitudinal layer is composed of three bands of muscle that run the length of the colon known as teniae. Diverticula occur in rows between the mesenteric and two antimesenteric teniae where the colonic wall is further weakened by the defect caused by the perforating vasa recti artery which supplies the colonic mucosa.
Occasionally, the anatomic propensity of diverticula to form in rows is quite apparent as seen when this clip is replayed in slow motion. Most often, however, the arrangement of the diverticula appears random due to the angulation of the bowel and thickening of the semi lunar folds. The conditions that cause these pulsion diverticula are not know with certainty but may include high intrahaustral pressures, muscular hypertrophy, and age related alterations in collagen cross linking. Diverticula can bleed or can abscess and perforate. The incidence of diverticulitis or diverticular bleeding is in the range of 1:1,000 patients with diverticulosis.
Peter B. Kelsey, M.D., Harvard Medical School, Massachusetts General Hospital