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Diverticulitis

By Joel A. Baum, MD, Assistant Clinical Professor of Medicine, Icahn School of Medicine at Mount Sinai ; Rafael Antonio Ching Companioni, MD, Icahn School of Medicine, Elmhurst Hospital Center

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Diverticulitis is inflammation, infection, or both of one or more balloon-like sacs (diverticula).

  • Diverticulitis usually affects the large intestine (colon).

  • Left lower abdominal pain, tenderness, and fever are the typical symptoms.

  • The diagnosis is based on the results of a computed tomography (CT) scan, and colonoscopy is done after the episode of diverticulitis is over.

  • People with mild diverticulitis symptoms are treated with rest, a liquid diet, and sometimes antibiotics given by mouth, whereas those with severe symptoms are hospitalized for treatment with antibiotics given by vein and sometimes surgery.

Diverticula of the colon occur when a defect develops in the thick, muscular middle layer of the large intestine. The thin inner layers of the bowel bulge out through the defect and create a small sac. One sac is a diverticulum.

Diverticulitis occurs in people with diverticulosis when a diverticulum develops a small (sometimes microscopic) hole that allows bacteria from the intestines to be released. Some doctors think that a diverticulum can become inflamed even if a hole has not developed. Diverticulitis most commonly affects the sigmoid colon, which is the last part of the large intestine just before the rectum.

Diverticulitis is more common among people older than 40. It can be severe in people of any age, although it is most serious in older people, especially those taking corticosteroids or other drugs that suppress the immune system and thus increase the risk of infection, including colon infection. Among people younger than 50 who must undergo surgery for diverticulitis, men outnumber women 3 to 1. Among people older than 70 who must undergo surgery for diverticulitis, women outnumber men 3 to 1.

Symptoms

Symptoms of diverticulitis typically include pain and/or tenderness (usually in the left lower part of the abdomen), fever, and sometimes nausea and vomiting. Diverticulitis typically does not cause gastrointestinal bleeding.

Complications of diverticulitis

Complications of diverticulitis include

  • Fistulas

  • Abscess

  • Peritonitis

A fistula is an abnormal channel connecting one organ with another or with the skin. Intestinal inflammation from diverticulitis can lead to the development of fistulas that connect the large intestine with other organs. Fistulas usually form when an inflamed diverticulum in the large intestine is touching another organ (such as the bladder). The resulting inflammation along with the bacterial contents of the large intestine slowly penetrate the nearby organ, resulting in a fistula. Most fistulas form between the sigmoid colon and the bladder. These fistulas are more common among men than women, although women who have had a hysterectomy (removal of the uterus) are at increased risk because the large intestine and bladder are no longer separated by the uterus. When fistulas form between the large intestine and bladder, intestinal contents, including normal bacteria, enter the bladder and cause urinary tract infections. Less commonly, a fistula can develop between the large intestine and the small intestine, uterus, vagina, abdominal wall, or even the thigh.

Complications of Diverticulitis

If a diverticulum ruptures, the contents of the intestine, including bacteria and blood, spill into the abdominal cavity, often causing infection. An abnormal channel (fistula) may form between the large intestine and another organ, usually when a diverticulum that touches another organ ruptures.

An abscess is a pocket of pus. An abdominal abscess can form around an inflamed diverticulum, causing worsened pain and fever.

Peritonitis is infection of the abdominal cavity, which can develop if the wall of a diverticulum ruptures.

Other possible complications of diverticulitis include inflammation of nearby organs (such as the uterus, bladder, or other areas of the digestive tract). Repeated bouts of diverticulitis can lead to intestine blockage because the resulting scarring and muscle thickening can narrow the inside of the large intestine and prevent solid stool from passing through.

Diagnosis

  • Computed tomography (CT) of the abdomen and pelvis

  • Colonoscopy after episode has ended

If a doctor knows that the person already has diverticulosis, a diverticulitis diagnosis may be based almost entirely on the symptoms. However, many other conditions involving the large intestine and other organs in the abdomen and pelvis can cause symptoms similar to diverticulitis, including appendicitis, colon cancer or ovarian cancer, an abscess, and noncancerous (benign) growths on the wall of the uterus (uterine fibroids).

A CT scan of the abdomen and pelvis may be helpful in determining that the problem is diverticulitis and not appendicitis or another diagnosis. Magnetic resonance imaging (MRI) is an alternative test for pregnant women or young people.

Once inflammation has subsided or the infection has been treated, a doctor does a colonoscopy (an examination of the large intestine using a flexible viewing tube). This test is done to rule out colon cancer. Colonoscopy usually needs to be delayed for 6 to 8 weeks after treatment because it can damage or rupture an inflamed intestine. Exploratory surgery is rarely needed to confirm the diagnosis.

Treatment

  • For mild diverticulitis, liquid diet and rest

  • For severe diverticulitis, no food or fluids by mouth and antibiotics

  • Sometimes surgery

Mild diverticulitis can be treated at home with rest, a liquid diet, and sometimes antibiotics given by mouth. Diverticulitis symptoms usually lessen rapidly. Some people do not need antibiotics for diverticulitis. After a few days, people can begin a fiber-rich diet. After 1 to 3 months, people have a colonoscopy to evaluate the colon.

Severe diverticulitis requires different treatment. People who have severe symptoms, such as abdominal pain, body temperature above 101° F (38.3° C), poor response to oral antibiotics, and other evidence of serious infection or complications, are hospitalized. In the hospital, people are given fluids and antibiotics by vein (intravenously), kept on bed rest, and given nothing by mouth until the symptoms subside.

For some people, antibiotics and rest are all that is needed to treat diverticulitis.

Drainage for abscesses

Larger abscesses are drained with a needle inserted through the skin and guided by a CT scan. If drainage helps, people remain in the hospital until symptoms have been relieved and they have resumed a soft diet. If drainage does not help, people need surgery.

Surgery for diverticulitis

Emergency surgery is necessary for people whose intestine has ruptured or who have peritonitis. Other people who need surgery include those who have severe diverticulitis symptoms that are not relieved by nonsurgical treatment (such as antibiotics) within 48 hours. People who have increasing pain, tenderness, and fever also need surgery.

The surgeon removes the involved section of the intestine. The ends are rejoined immediately in healthy people who do not have a perforation, abscess, or severe intestinal inflammation. Other people need a temporary colostomy. A colostomy is an opening between the large intestine and the skin surface. About 10 to 12 weeks later (or sometimes longer), after the inflammation has gone away and the person's condition has improved, the cut ends of the intestine are rejoined during a follow-up operation, and the colostomy is closed.

Understanding Colostomy

In a colostomy, the large intestine (colon) is cut. The part that remains connected to the colon is brought to the skin surface through an opening that has been formed. The part is then stitched to the skin. Stool passes through the opening and into a disposable bag.

Fistula treatment involves removing the section of large intestine where the fistula begins, rejoining the cut ends of the large intestine, and repairing the other affected area (for example, the bladder or small intestine).

Diverticulitis: Examples of Reasons for Elective Surgery

Condition

Reason

Three or more attacks of mild diverticulitis (or one attack in someone younger than 50)

High risk of serious complications

Narrowing of the sigmoid colon (lower part of the large intestine) due to scarring

High risk of serious complications

Persistent tender mass in the abdomen

May be cancer

Endoscopy or x-rays showing suspicious changes in the sigmoid colon

May be cancer

Pain when urinating (dysuria) or air in the urine (pneumaturia)

May be a warning of impending fistula formation between the large intestine and the bladder

Sudden abdominal pain in people taking corticosteroids

Large intestine may have ruptured into the abdominal cavity

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