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Irritable Bowel Syndrome

What Is Irritable Bowel Syndrome?

Irritable bowel syndrome (IBS) is the most common gastrointestinal disorder in the United States. It is characterized by intermittent periods of constipation or diarrhea and often pain or bloating. After partly digested food leaves the stomach, it is moved through the small and then the large intestine by regular contractions (peristaltic motility) of the muscles in the intestinal wall. In IBS, these muscles may go into spasm and move residues either too quickly (causing diarrhea) or too slowly (causing constipation). IBS should not be confused with the more serious inflammatory bowel diseases.

There is no cure for IBS; treatment focuses on relief of symptoms, which can often be accomplished with a combination of diet and stress management. Medications are also sometimes helpful. IBS is more common in women than men, and symptoms may worsen in relation to menses.

Who Gets Irritable Bowel Syndrome?

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), IBS symptoms occur in about 20% of people in the United States. Up to 30% of people in the United States experience symptoms of IBS at some point during their lifetime. In about half of all cases, symptoms occur before the age of 35. Irritable bowel syndrome is approximately twice as common in women as in men.


Symptoms vary from person to person and are often triggered by a particular food, stressful event, or bout of depression. The most common symptoms include: .

  • Constipation or diarrhea, or alternating bouts of both. Sometimes bouts of both lasting for days, weeks or months (Diarrhea may occur immediately after awakening in the morning or right after eating and may contain white mucus.).

  • Abdominal discomfort, pain, bloating, or cramps. (Pain is often relieved by a bowel movement.) .

  • Excess gas.

  • A feeling that the bowels do not empty completely.

  • Nausea.

  • A worsening of symptoms after eating a big meal, during menstrual periods, or when you are under stress.

  • Lactose intolerance—the inability to digest lactose (milk sugar), caused by an enzyme deficiency—can also produce the same symptoms.

Causes/Risk Factors

  • The cause of IBS is unknown, though it is felt to be a disorder of gastrointestinal motility (a disorder of the function of the gastrointestinal tract rather than a structural problem).

  • Emotional stress may be a contributing factor.

  • Certain foods may trigger flare-ups. Common irritants include high-fat foods such as bacon, poultry skin, vegetable oils, and margarine; dairy products; and gas-producing foods such as beans and broccoli.

Researchers are investigating several possible causes for IBS. For example:

  • Hormonal changes may be a factor for women, since symptoms can worsen during menstrual periods.
  • The neurotransmitter serotonin, which transmits messages between parts of the body and is involved in sleep-waking cycles, is also present in the lining of the gastrointestinal tract. High levels of serotonin might cause a patient to be more sensitive to abdominal pain if signals between the brain and the intestines misfire.
  • The central nervous system can affect intestinal contractions.
  • The immune system and bacterial infections may be involved, since some patients who have gastroenteritis (infectious diarrhea) eventually develop IBS.
  • Celiac disease (also called celiac sprue) may contribute to IBS. Celiac sprue is an intestinal tract disease caused by difficulty digesting proteins found in wheat (e.g., gluten). Celiac disease causes an inadequate absorption of nutrients and weight loss, and may cause IBS symptoms.

What If You Do Nothing?

It’s estimated that half of the people with IBS don’t seek medical attention and choose instead to live with their “nervous stomach” because their IBS symptoms aren’t that bothersome.

Although the disorder can cause much discomfort, it does not lead to serious disease. If you can learn to control the chronic flare-ups and relieve the often bothersome symptoms of IBS yourself, you can probably keep the condition from interfering with your everyday activities.


  • Patient history and physical examination are needed. Diagnosis is made by ruling out other disorders, such as cancer and inflammatory bowel diseases.
  • A barium enema may be necessary. Barium creates a clear image of the colon on an x-ray.
  • A small, lighted viewing tube may be used to inspect part (sigmoidoscopy) or all (colonoscopy) of the large intestine.

Once your doctor determines that your abdominal pain is not due to a physical abnormality, two of the following three criteria must be met to make a diagnosis of IBS:

  • bowel movements alleviate pain
  • pain is accompanied by constipation or diarrhea
  • pain is associated with a change in the form of the stool (watery, loose, or pellet-like)

These symptoms must be present, all of the time or occasionally, for at least three months.

Because the symptoms of IBS overlap with so many other digestive disorders, people with the syndrome are sometimes misdiagnosed. IBS can easily be confused with:

  • diverticulitis
  • colon cancer
  • intestinal obstruction
  • ulcerative colitis
  • Crohn's disease
  • gastrointestinal infection
  • celiac disease
  • lactose intolerance


  • A low-fat diet is recommended (high-fat foods may aggravate symptoms).

  • Experiment with fiber intake in the diet. Some people find that symptoms are relieved by a diet rich in high-fiber foods (raw fruits and vegetables, bran, whole-grain breads, and dried legumes). Others find that a high-fiber diet increases symptoms.

  • Smaller, more frequent meals may be easier to digest.

  • Try eliminating gas-forming foods. If your pre-dominant symptom is gas, eliminating beans, peas, lentils, broccoli, cauliflower, onions, cucumbers, and leafy vegetables may help. If symptoms improve, gradually reintroduce these foods and see what happens.

  • Don’t delay. If you feel the urge to move your bowels, do so. Any delay may contribute to becoming constipated.

  • Smoking may act as a trigger and should be avoided.

  • Psychological counseling, meditation, or biofeedback may aid in the management of stress. Regular, moderate exercise may also reduce stress and relieve symptoms.

  • Your doctor may prescribe laxatives, antidiarrheal medications, antispasmodics, bulk-forming agents (psyllium), antibiotics, or antidepressants.

  • Several medications are approved specifically for treating IBS symptoms. Linaclotide (Linzess) may help relieve constipation and pain associated with IBS, and lubiprostone (Amitiza) is approved for use in women who have constipation-predominant IBS. Alosetron (Lotronex) is a special drug intended for severe cases of diarrhea-predominant IBS in women who haven’t responded to other treatments; it requires careful monitoring because of the potential for rare but serious side effects. Two other medications for treating IBS with diarrhea have recently been approved by the FDA and will soon be available.


There is no known way to prevent irritable bowel syndrome; however, symptomatic episodes can often be minimized through dietary modifications and stress management techniques.

When To Call Your Doctor

Make an appointment with your doctor if symptoms of IBS interfere with normal activities. Your doctor can also check for more serious disorders such as gallstones, diverticular disorders, colon cancer, ulcers, and bacterial and other infections.

Reviewed by Jenifer K. Lehrer, M.D., Department of Gastroenterology, Aria-Torresdale Hospital, Aria Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network.