Irritable Bowel Syndrome

Aria Health Center for Gynecology & Women's Health

Irritable Bowel Syndrome (IBS) is a common condition, manifested by a disruption of muscle movements of the intestines. These abnormal muscle contractions in the colon cause cramping and a dysfunction in motility (ability of the large bowel to move fecal matter normally). The result is pain and other discomfort, as well as irregular bowel movements. While the condition can cause a great deal of discomfort and distress, it is not believed to cause permanent harm to the intestines, lead to intestinal bleeding of the bowel, or be a risk factor or precondition for more serious diseases such as inflammatory bowel disease or cancer.

The digestion and propulsion of nutrients and fluids through the gastrointestinal system is a complicated and well-organized process. The GI tract has its own intrinsic muscles and nerves that connect, like an electrical circuit, to the spinal cord and brain. Neuromuscular events occurring in the GI tract are relayed to the brain through neural connections, and the response of the brain is also relayed back to the gastrointestinal tract. As a result of this activity, motility and sensation in the bowel are generated. An abnormality in this process leads to disordered propulsion of the intestinal contents and pain.

The person with IBS has a colon that is more sensitive and reactive than usual, so it responds strongly to stimuli that would not affect others. The colon muscles of a person with IBS begin to spasm after only mild stimulation or ordinary events such as the following:

  • eating;
  • distention from gas or other material in the colon;
  • certain medications;
  • and certain foods.

Women with IBS seem to have more symptoms during their menstrual periods, suggesting that reproductive hormones can increase IBS symptoms.

Causes/risk factors

Why certain people develop this condition is unknown. Two likely triggers, though, for people who have the condition or a predisposition to it are:

  • diet, because the amount of fat in the diet, types of foods, time since the last meal, and other factors related to eating influence contractions in the colon and rhythm of the intestinal movements or lack thereof;
  • and stress, because this factor can somehow stimulate colonic spasm in IBS, presumably because both stress and intestinal motility are mediated by the nervous system.

Signs & symptoms

The physical symptoms of IBS include:

  • crampy abdominal pain;
  • gassiness;
  • bloating;
  • changes in bowel function causing diarrhea or constipation, sometimes in alternation;
  • nausea before or after bowel movements;
  • and mucus in the feces.


IBS is functional condition rather than an anatomic one, meaning that direct evidence of the disorder cannot normally or easily be seen through imaging or otherwise inspecting the bowel but only by taking a history of the patient's signs and symptoms. Physicians may order other lab tests or imaging studies, however, to eliminate the possibility of other and especially more serious conditions.


Symptoms of IBS can vary fairly widely between patients; therefore, treatment is often tailored to the individual's experience. For example, care for this condition may vary depending on whether a patient has diarrhea-predominant or constipation-predominant IBS. Treatment approaches include:

  • Medications. Physicians may suggest a trial of a drug with an antidepressant or tranquilizing function. Newer drug studies are fine-tuning our ability to match a patient with a potentially helpful medication for IBS. In 2002, the FDA approved tegaserod (Zelnorm), which is targeted to patients with constipation-predominant IBS. Zelnorm reduces constipation by increasing contractions of the intestinal muscles. The most widely used drug for diarrhea-predominant IBS is loperamide (Imodium). Alosetron (Lotronex) is also used to treat diarrhea and abdominal discomfort that occurs in women with severe IBS that does not respond to other simpler treatments. Smooth-muscle relaxants such as hyoscyamine (Levsin) and methscopolamine (Pamine) are also sometimes effective, especially for patients whose primary symptom is abdominal pain. Other types of drugs are currently under study for IBS.
  • Diet. The connection of diet to severity of IBS symptoms is unclear. Some patients claim relief as a result of modifying diet. And physicians traditionally suggested trying diets that are high in fiber (especially for constipation-predominant IBS) or low in fat, or both. Keeping a list of foods that seem connected to your IBS distress, and discussing the findings with a physician or registered dietitian, can help. Testing for lactose intolerance has also helped some people.
  • Stress reduction. Counseling and stress reduction techniques can help relieve symptoms of IBS for some patients; however, this does not mean IBS is the result of a psychological problem. It is at least partly an inherent disorder of colon motility.

In addition, your physician may also recommend regular exercise, which also appears to help moderate symptoms of IBS for some people.