Diverticulosis of the sigmoid colon with peridiculoid fibrosis and colonic muscular wall hyperplasia.clinical symptoms: 74-year old patient with stenosing and penetrating rectosigmoid diverticulitis. State after urosepsis due to proven colovesical fistula. commentary: In most cases the diverticula are false meaning that only the mucosa and submucosa are involved. The outpouching occurs through the muscular layer at the points where the vessels pass through. The cause for the outpouching is increased intraluminal pressure and presumably a genetical predisposition. Source: ©PathoPic