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Irritable bowel syndrome

Definition

Irritable bowel syndrome (IBS) refers to a disorder that involves abdominal pain and cramping, as well as changes in bowel movements.

It is not the same as inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis.

Alternative Names

Spastic colon; Irritable colon; Mucous colitis; Spastic colitis

Causes, incidence, and risk factors

There are many possible causes of IBS. For example, there may be a problem with muscles in the intestine, or the intestine may be more sensitive to stretching or movement. There is no problem with the structure of the intestine.

It is not clear why patients develop IBS, but in some instances, it occurs after an intestinal infection. This is called postinfectious IBS. There may also be other triggers.

Stress can worsen IBS. The colon is connected to the brain through nerves of the autonomic nervous system. These nerves become more active during times of stress, and can cause the intestines to squeeze or contract more. People with IBS may have a colon that is over-responsive to these nerves.

IBS can occur at any age, but it often begins in adolescence or early adulthood. It is more common in women. About 1 in 6 people in the U.S. have symptoms of IBS. It is the most common intestinal complaint for which patients are referred to a gastroenterologist.

Symptoms

Symptoms range from mild to severe. Most people have mild symptoms. Symptoms vary from person to person.

Abdominal pain, fullness, gas, and bloating that have been present for at least 6 months are the main symptoms of IBS. The pain and other symptoms will often:

  • Occur after meals
  • Come and go
  • Be reduced or go away after a bowel movement

People with IBS may switch between constipation and diarrhea, or mostly have one or the other.

  • People with diarrhea will have frequent, loose, watery stools. They will often have an urgent need to have a bowel movement, which is difficult to control.
  • Those with constipation will have difficulty passing stool, as well as less frequent bowel movements. They will often need to strain and will feel cramping with a bowel movement. Often, they do not eliminate any stool, or only a small amount.

For some people, the symptoms may get worse for a few weeks or a month, and then decrease for a while. For other people, symptoms are present most of the time and may even slowly increase.

People with IBS may also lose their appetite.

Signs and tests

Most of the time, your doctor can diagnose IBS based on your symptoms, with few or no tests. Eating a lactose-free diet for 2 weeks may help the doctor evaluate for a possible lactase deficiency.

There is no test to diagnose IBS, but tests may be done to rule out other problems:

  • Blood tests to see if you have a low blood count (anemia)
  • Stool cultures to rule out an infection

Some patients will have sigmoidoscopy or colonoscopy. During these tests, a hollow tube is inserted through the anus. The doctor can see through this tube. You may need these tests if:

  • Symptoms began later in life (over age 50)
  • You have symptoms such as weight loss or bloody stools
  • You have abnormal blood tests (such as a low blood count)

Other disorders that can cause similar symptoms include:

Treatment

The goal of treatment is to relieve symptoms.

Lifestyle changes can be helpful in some cases of IBS. For example, regular exercise and improved sleep habits may reduce anxiety and help relieve bowel symptoms.

Dietary changes can be helpful. However, no specific diet can be recommended for IBS in general, because the condition differs from one person to another. The following changes may help:

  • Avoid foods and drinks that stimulate the intestines (such as caffeine, tea, or colas)
  • Avoid large meals
  • Avoid wheat, rye, barley, chocolate, milk products, and alcohol
  • Increase dietary fiber

Talk with your doctor before taking over-the-counter medications.

  • Fiber supplements can make symptoms worse
  • Laxatives taken for constipation can become habit forming

No one medication will work for everyone. Medications your doctor might try include:

  • Anticholinergic medications (dicyclomine, propantheline, belladonna, and hyoscyamine) taken about a half-hour before eating to control colon muscle spasms
  • Loperamide to treat diarrhea
  • Low doses of tricyclic antidepressants to help relieve intestinal pain
  • Lubiprostone for constipation symptoms
  • Medications that relax muscles in the intestines

Counseling may help in cases of severe anxiety or depression.

Expectations (prognosis)

Irritable bowel syndrome may be a lifelong condition. For some people, symptoms are disabling and reduce the ability to work, travel, and attend social events.

Symptoms can often be improved or relieved through treatment.

IBS does not cause permanent harm to the intestines, and it does not lead to a serious disease, such as cancer.

Calling your health care provider

Call your health care provider if you have symptoms of irritable bowel syndrome or if you notice a persistent change in your bowel habits.

References

Talley NJ. Irritable bowel syndrome. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 118.

Irritable bowel syndrome. NIH Publication No. 07-693. September 2007. The National Digestive Diseases Information Clearinghouse (NDDIC).


Review Date: 7/7/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, Unviersity of Washington School of Medicine; and George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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