University of Iowa Health Science Relations and
Satish Rao, MBBS, PhD
Professor of Internal Medicine
First Published: November 2000
Last Revised: December 2003
Peer Review Status: Internally Peer Reviewed

Irritable bowel syndrome is unlike any other gastrointestinal disorder. It is a poorly defined syndrome, because in order to diagnose the condition, you have to rule out more serious medical problems.

"IBS mimics pains and other symptoms caused by ulcers, colitis, colonic cancer, and other bowel diseases," says Dr. Satish Rao, professor of gastroenterology and director of neurogastroenterology and GI motility at the University of Iowa College of Medicine and staff physician at UI Hospitals and Clinics.

It is the most common gastrointestinal disorder. Of the people who are referred to a gastroenterology clinic, half are diagnosed with functional gastrointestinal disorders, among which IBS is prominent. For unknown reasons, women are twice as likely as men to have the condition.

What causes IBS is not known for certain, but Rao believes that psychological problems can play a role. "People stressed by problems at work, home, or from an illness seem to have a higher incidence of IBS symptoms," he says. Half of the patients with IBS date the first occurrence of their symptoms to an episode of stress or previous gastroenteritis, he adds. More recent research suggests that hypersensitivity of the gut and a dysfunction of how the brain processes gut signals may play a crucial role.

Symptoms of IBS include pain, bloating, constipation, and diarrhea:

• Pain can occur in the esophagus, stomach, rectum, back, or lower ribs.
• A change in bowel habit is another common IBS symptom. The person may experience constipation or diarrhea, or alternating episodes of both. "Eating a diet rich in fiber helps digestion. Without fiber, the food reaching the colon has very little bulk and cannot retain water. This makes bowel movement difficult and painful," Rao says.
• Bloating is also a common problem among people with IBS. "In some patients, bloating may be due to a deficiency of the enzymes needed to digest certain foods. If undigested food, particularly carbohydrates, are dumped into the colon, excess gas production occurs," Rao says. Common food products include lactose and fructose. Also, in some patients excesive growth of bacteria in the small bowel may cause IBS symptoms.

Once IBS has been diagnosed--and other serious medical conditions ruled out--treatments may include an antispasmodic medication and/or changes in diet, Rao explains. "If the problem is a lack of fiber, the physician will encourage the person to increase the amount of vegetables and fresh fruit in his or her diet."

Some people may be intolerant to specific foods, which can cause the symptoms of IBS, Rao adds. "The physician will suggest the person eat one food for a day, and then add other foods in the next days. By gradually reintroducing foods, it will be possible to identify the troublesome food."

Recent research from Iowa has shown that up to 30 percent of patients with chronic IBS may have fructose intolerance--a common fruit/vegetable-based sugar.

An international group of experts has recently established Diagnostic Criteria (Rome II) for IBS. Recently, drugs that relatively improve IBS symptoms have become available.

For more information about irritable bowel syndrome, talk to your physician.