DIVERTICULITIS
Diverticula, serosa-covered saccules that include mucosa, extend from the lumen through thecolonic muscular layer and are very common in later life in Western societies. These small herniations occur usually through areas of the colonic wall weakened by penetration of an arteriole. The incidence of diverticula is thought to be enhanced by any factor that chronically increases intraluminal pressure, particularly by refined diets of low fiber content that yield stools of small bulk. Most diverticula are found in the sigmoid area and are asymptomatic. They become important because of two complications: bleeding and infection. Vessels in or around a diverticulum may bleed briskly in older people, and diverticular bleeding must be differentiated from bleeding from other causes, especially from angiodysplasia or carcinoma. The differential diagnosis of gastrointestinal bleeding is discussed in Chapter 36B. Diverticulitis refers specifically to infection in or around diverticula, thought to result usually from obstruction by fecoliths or inspissated feces with impairment of the blood supply and drainage. This walled-off, localized infection, caused by intestinal organisms, may produce a microabscess that heals spontaneously, may perforate to cause localized or more rarely generalized peritonitis, or may extend to cause larger abscesses that may be local or that may rarely penetrate other adjacent organs. Acute diverticulitis is said to simulate “left-sided appendicitis” with left lower quadrant pain (often exacerbated during defecation), tenderness, fever, leukocytosis, and sometimes a palpable inflammatory mass. Bleeding during the acute illness, if present at all, is usually microscopic. Rectal examination may reveal a tender mass; sigmoidoscopy characteristically shows extrinsic narrowing of the colonic lumen and inflamed mucosa. Barium enema,which is hazardous during the acute phase, generally confirms the presence of an inflammatory mass and often shows leakage of barium beyond the lumen of a diverticulum. The acute illness is treated by withholding solid food and by the use of broad-spectrum antibiotics. Surgical treatment may be required acutely for perforation, fistula formation, or a large abscess and electively for recurrent attacks of diverticulitis, especially when these result in fibrosis and obstruction. Mam-physicians recommend high-fiber diets to reduce colonic intraluminal pressures in an attempt to prevent the progression of diverticulosis and the recurrence of diverticulitis.