Most people have, in their colons, small pouches that bulge outward through weak spots, like an inner tube that pokes through weak places in a tire. Each pouch is called a diverticulum. Pouches are diverticula. The condition of having diverticula is called diverticulosis. About half of all Americans age 60 to 80, and almost everyone over age 80, have diverticulosis. When the pouches become infected or inflamed, the condition is called diverticulitis. Diverticulosis and diverticulitis are also called diverticular disease.

What Causes Diverticulosis?

A low-fiber diet may be the main cause of diverticulosis. The condition was first noticed in the United States in the early 1900's, at about the same time processed foods were introduced to the American diet. Many processed foods contain refined, low-fiber flour. Unlike whole-wheat flour, refined flour has no wheat bran.

Diverticulosis is common in developed or industrialized countries — particularly the United States, England, and Australia—where low-fiber diets are common. The condition is much less common in Asia and Africa, where people eat high-fiber vegetable diets.

Fiber is present in many fruits, vegetables, and grains. Fiber prevents constipation. When stools are hard and difficult to pass the muscles of the colon strain to move stool that is too hard. This increases the pressure within the colon. The excess pressure may causes weak spots in the colon to bulge out and become diverticula.

Diverticulitis occurs when diverticula become inflamed and infected. Doctors are not certain what causes this to happen. It may begin when hard stool gets caught in the diverticula.

What are the Symptoms?

Most people with diverticulosis do not have any symptoms. The diagnosis is made when they undergo colonoscopy for other reasons, frequently during routine colon cancer screening. Sometimes diverticulosis is a cause of gastrointestinal bleeding and presents with blood in the stool. Constipation, bloating, and abdominal discomfort may occur in patients with diverticulosis. Usually, these symptoms are not caused by diverticulosis.

The most common symptom of diverticulitis is cramping abdominal pain usually associated with fever and sometimes with constipation. Tenderness is often present around the left side of the lower abdomen. The severity of symptoms depends on the extent of the infection and whether complications develop.

Are There Complications?

Diverticulitis can lead to complications such as abscess formation, perforation (or holes), blockages, or bleeding. These complications always require treatment to prevent them from progressing and causing serious illness.

Bleeding from diverticula is a rare complication. When diverticula bleed, blood may appear in the toilet or in your stool. Bleeding can be severe, but it may stop by itself and not require treatment. Doctors believe bleeding diverticula are caused by a small blood vessel in
a diverticulum that weakens and bursts. If you have bleeding from the rectum, you should see your doctor. If the bleeding does not stop, surgery may be necessary.

Abscess, Perforation, and Peritonitis
Abscess formation may complicate severe acute diverticulitis. An abscess is an area of infection that fills with pus. Pus under pressure will cause fever and pain. Abscesses associated with diverticulitis are serious. Treatment with antibiotics may clear up a small abscess but larger collections of pus require drainage, either by placing a drainage tube into the abscess or by surgery. Untreated, an abscess may perforate leading to infection spreading into the abdominal cavity. This is called peritonitis.

A fistula is an abnormal connection or tract between two organs or between an organ and the skin. When damaged tissues come into contact with each other during infection, they sometimes stick together. If they heal that way, a fistula forms. When diverticulitis-related infection spreads outside the colon, the colon's tissue may stick to nearby tissues. The most common organs involved are the urinary bladder, small intestines, and skin. The most common type of fistula occurs between the bladder and the colon. This type of fistula can result in a severe, long-lasting infection of the urinary tract. The problem can be corrected with surgery to remove the fistula and the affected part of the colon.

Intestinal Obstruction
The scarring caused by the infection may cause partial or total blockage of the large intestine. When this happens, the colon is unable to move bowel contents normally. When the obstruction totally blocks the intestine, emergency surgery is necessary. Partial blockage is not an emergency, so the surgery to correct it can be planned.

How Does the Doctor Diagnose Diverticulosis?

Because most people do not have symptoms, diverticulosis is often found when tests are performed for other conditions or during routine colon cancer screening tests.

What Is the Treatment for Diverticulosis?

Most patients with diverticulosis do not require treatment. However, increasing the amount of fiber in the diet and drinking plenty of water is very helpful in treating constipation and abdominal cramping when this is associated with diverticulosis. Fiber keeps stools soft and lowers pressure inside the colon so that bowel contents can move through easily. The American Dietetic Association recommends 20 to 35 grams of fiber each day. In addition to eating more fruits, vegetables and fiber, your doctor may recommend using a fiber product such as psyllium (Metamucil®) or Benefiber® every day. These products are mixed with water and provide about 4–6 grams of fiber for an 8-ounce glass.

What Is the Treatment for Diverticulitis?

Treatment for diverticulitis focuses on cleaning up the infection, resting the colon and preventing or minimizing complications. A mild attack of diverticulitis, without complications, may respond to antibiotics taken by mouth. To help the colon heal, the doctor may recommend bed rest and a liquid diet, along with a pain reliever or a drug to control muscle spasms in the colon. A severe attack may require a hospital stay with antibiotics given by injection into a vein. In some cases surgery may be necessary.

From Your Physician

The National Digestive Diseases Information Clearinghouse, a service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Public Health Service, has prepared this information.