The pathology of diverticulosis: classical concepts and mucosal changes in diverticula.

Left-sided diverticular disease affects upwards of 50% of the population over the age of 60 years in western countries and is becoming more common as the population ages. Studies from the 1960s to 1980s related its occurrence to the use of low fiber diets, and to the prolonged colonic transit time and increased intraluminal pressure associated with low-volume stools. Pulsion diverticula (pseudodiverticula) emerge through the muscularis propria of the left colon at points of penetration of the vasa recta that supply the submucosa and mucosa. Cardinal features of the sigmoid colon in diverticular disease are abnormalities of the muscularis propria, including thickening and elastosis of the teniae, shortening of the bowel, and thickening and folding of the circular muscle with the development of transverse semilunar ridges between the mesenteric and antimesenteric teniae. Complications of diverticular disease such as hemorrhage, diverticulitis, peridiverticular abscess, fistula, and perforation are well recognized.