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

Causes, incidence, and risk factors

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, specifically the sigmoid colon. These sacs, called diverticula, occur with increasing frequency 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 distribution within the colon. High pressure exerted against the colon wall causes pouches of the intestinal lining to bulge outwards through small defects in the colon wall.

Diverticulosis is very common, being 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 perforation within a diverticulum. If the perforation is large, stool in the colon can spill into the abdominal cavity, causing an abscess or peritonitis.

Direct risk factors for diverticulitis are not known. 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 and vomiting

Signs and tests

Tests showing diverticulitis may include:

  • CT scan revealing thickening of the inflamed area  
  • Abdominal palpation showing left lower quadrant mass  
  • Elevated white blood cell count

Tests such as colonoscopy, sigmoidoscopy, and barium enema are usually not performed if diverticulitis is suspected.


Acute diverticulitis requires antibiotic therapy.

Recurrent attacks or presence of perforation, fistula (abnormal tube-like passage), or abscess requires surgical removal of the involved portion of the colon.

After the acute infection has stabilized, diverticulitis is treated by increasing the bulk in the diet with high-fiber foods and bulk additives such as psyllium.

Expectations (prognosis)

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


  • Abscess formation  
  • Perforation of the colon leading to peritonitis  
  • Stricture or fistula formation

Calling your health care provider

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. Many people, including 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.

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

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