Diverticulitis is swelling (inflammation) of an abnormal pouch (diverticulum) in the intestinal wall. These pouches are usually found in the large intestine (colon). The presence of the pouches themselves is called diverticulosis.

Small, protruding sacs of the inner lining of the intestine (diverticulosis) can develop in any part of the intestine. They are most common in the colon, especially the sigmoid colon, the lowest part of the colon.

These sacs, called diverticula, occur more often after the age of 40. When they become inflamed, the condition is known as diverticulitis. Diverticula are thought to develop as a result of high pressure or abnormal pressure in the colon. High pressure against the colon wall causes pouches of the intestinal lining to bulge outward through small defects in the colon wall that surround blood vessels.

Diverticulosis is very common. It is found in more than half of Americans over age 60. Only a small percentage of these people will develop the complication of diverticulitis.

Diverticulitis is caused by inflammation, or (sometimes) a small tear in a diverticulum. If the tear is large, stool in the colon can spill into the abdominal cavity, causing an infection (abscess) or inflammation in the abdomen.

Risk factors for diverticulosis may include older age or a low-fiber diet.

• Abdominal pain, usually in the left lower abdomen but can be anywhere
• Chills
• Fever
• Nausea
• Vomiting
• Weight loss

Tests showing diverticulitis may include:

• Abdominal palpation
• CT scan
• High white blood cell count

Acute diverticulitis is treated with antibiotics.

The involved portion of the colon may need to be removed with surgery if you have:

• Abscess
• Hole (perforation) in the colon
• Fistula (abnormal connections between different parts of the colon or the colon and another body area)
• Repeated attacks of diverticulitis

After the acute infection has improved, eating high-fiber foods and using bulk additives such as psyllium may help reduce the risk of diverticulitis or other symptoms.

Usually, this is a mild condition that responds well to treatment.

• Abscess formation
• Narrowing (stricture) in the colon or fistula formation
• Perforation of the colon leading to peritonitis

Call your health care provider if symptoms of diverticulitis occur.

Also call if you have diverticulitis and symptoms worsen or new symptoms develop.

A high-fiber diet may prevent development of diverticulosis. Some doctors tell patients with a history of diverticulitis to avoid nuts and seeds in the diet. However, there is no evidence that this is helpful to prevent the disease.

Prather C. Inflammatory and anatomic diseases of the intestine, peritoneum, mesentery, and omentum. In: Goldman L, Ausiello D. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 145.