Causes

It is not clear why patients develop IBS. Sometimes it occurs after an infection of the intestines. This is called postinfectious IBS. There may also be other triggers.

The intestine is connected to the brain. Signals go back and forth between the bowel and brain. These signals affect bowel function and symptoms. The nerves can become more active during stress, causing the intestines to be more sensitive and squeeze (contract) more.

IBS can occur at any age, but it often begins in the teen years or early adulthood. It is twice as common in women as in men.

About 1 in 6 people in the U.S. have symptoms of IBS. It is the most common intestinal problem that causes patients to be referred to a bowel specialist (gastroenterologist).

Symptoms

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

The main symptoms of IBS are abdominal pain, fullness, gas, and bloating that have been present for at least 3 days a month for the last 3 months. The pain and other symptoms will often:

• Be reduced or go away after a bowel movement
• Occur when there is a change in how often you have bowel movements

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 may be hard to control.
• Those with constipation will have a hard time passing stool, as well as fewer bowel movements. They will often need to strain and will feel cramps with a bowel movement. Often, they do not release 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.

People with IBS may also lose their appetite.

Exams 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 check for a possible lactase deficiency.

There is no test to diagnose IBS. Tests may be done to rule out other problems:

• Blood tests to see if you have celiac disease or a low blood count (anemia)
• Stool cultures to check for an infection

Some patients will have colonoscopy. During this test, a flexible tube is inserted through the anus to examine the colon. You may need this test 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:

• Celiac disease
• Colon cancer (cancer rarely causes typical IBS symptoms, unless symptoms such as weight loss, blood in the stools, or abnormal blood tests are also present)
• Crohn's disease or ulcerative colitis

Treatment

The goal of treatment is to relieve symptoms.

Lifestyle changes can help 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, 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
• Increase fiber in the diet (this may improve constipation but make bloating worse)

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

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 intestine muscle spasms
• Bisacodyl to treat constipation
• Loperamide to treat diarrhea
• Low doses of tricyclic antidepressants to help relieve intestinal pain
• Lubiprostone for constipation symptoms
• Rifaximin, an antibiotic

Therapy may help in cases of severe anxiety or depression.

Outlook (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.

When to Contact a Medical Professional

Call your health care provider if you have symptoms of irritable bowel syndrome or if you notice a change in your bowel habits that does not go away.

Alternative Names

Spastic colon; Irritable colon; Mucous colitis; Spastic colitis

References

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

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.

Update Date: 4/22/2012

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University 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.