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Irritable bowel syndrome


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Irritable bowel syndrome
From Gale Encyclopedia of Medicine, 4/6/01 by Howard Baker


Irritable bowel syndrome (IBS) is a common intestinal condition characterized by abdominal pain and cramps; changes in bowel movements (diarrhea, constipation, or both); gassiness; bloating; nausea; and other symptoms. There is no cure for IBS. Much about the condition remains unknown or poorly understood; however, dietary changes, drugs, and psychological treatment are often able to eliminate or substantially reduce its symptoms.


IBS is the name people use today for a condition that was once called--among other things--colitis, mucous colitis, spastic colon, nervous colon, spastic bowel, and functional bowel disorder. Some of these names reflected the now outdated belief that IBS is a purely psychological disorder, a product of the patient's imagination. Although modern medicine recognizes that stress can trigger IBS attacks, medical specialists agree that IBS is a genuine physical disorder--or group of disorders--with specific identifiable characteristics.

No one knows for sure how many Americans suffer from IBS. Surveys indicate a range of 10-20%, with perhaps as many as 30% of Americans experiencing IBS at some point in their lives. IBS normally makes its first appearance during young adulthood, and in half of all cases symptoms begin before age 35. Women with IBS outnumber men by two to one, for reasons that are not yet understood. IBS is responsible for more time lost from work and school than any medical problem other than the common cold. It accounts for a substantial proportion of the patients seen by specialists in diseases of the digestive system (gastroenterologists). Yet only half--possibly as few as 15%--of IBS sufferers ever consult a doctor.

Causes & symptoms


The symptoms of IBS tend to rise and fall in intensity rather than growing steadily worse over time. They always include abdominal pain, which may be relieved by defecation; diarrhea or constipation; or diarrhea alternating with constipation. Other symptoms--which vary from person to person--include cramps; gassiness; bloating; nausea; a powerful and uncontrollable urge to defecate (urgency); passage of a sticky fluid (mucus) during bowel movements; or the feeling after finishing a bowel movement that the bowels are still not completely empty. The accepted diagnostic criteria--known as the Rome criteria--require at least three months of continuous or recurrent symptoms before IBS can be confirmed. According to Christine B. Dalton and Douglas A. Drossman in the American Family Physician, an estimated 70% of IBS cases can be described as "mild;" 25% as "moderate;" and 5% as "severe." In mild cases the symptoms are slight. As a general rule, they are not present all the time and do not interfere with work and other normal activities. Moderate IBS occasionally disrupts normal activities and may cause some psychological problems. People with severe IBS often find living a normal life impossible and experience crippling psychological problems as a result. For some the physical pain is constant and intense.


Researchers remain unsure about the cause or causes of IBS. It is called a functional disorder because it is thought to result from changes in the activity of the major part of the large intestine (the colon). After food is digested by the stomach and small intestine, the undigested material passes in liquid form into the colon, which absorbs water and salts. This process may take several days. In a healthy person the colon is quiet during most of that period except after meals, when its muscles contract in a series of wavelike movements called peristalsis. Peristalsis helps absorption by bringing the undigested material into contact with the colon wall. It also pushes undigested material that has been converted into solid or semisolid feces toward the rectum, where it remains until defecation. In IBS, however, the normal rhythm and intensity of peristalsis is disrupted. Sometimes there is too little peristalsis, which can slow the passage of undigested material through the colon and cause constipation. Sometimes there is too much, which has the opposite effect and causes diarrhea. A Johns Hopkins University study found that healthy volunteers experienced 6-8 contractions of the colon each day, compared with up to 25 contractions a day for volunteers suffering from IBS with diarrhea, and an almost complete absence of contractions among constipated IBS volunteers. In addition to differences in the number of contractions, many of the IBS volunteers experienced powerful spasmodic contractions affecting a larger-than-normal area of the colon--"like having a Charlie horse in the gut," according to one of the investigators.


Some kinds of food and drink appear to play a key role in triggering IBS attacks. Food and drink that healthy people can ingest without any trouble may disrupt peristalsis in IBS patients, which probably explains why IBS attacks often occur shortly after meals. Chocolate, milk products, caffeine (in coffee, tea, colas, and other drinks), and large quantities of alcohol are some of the chief culprits. Other kinds of food have also been identified as problems, however, and the pattern of what can and cannot be tolerated is different for each person. Characteristically, IBS symptoms rarely occur at night and disrupt the patient's sleep.


Stress is an important factor in IBS because of the close nervous system connections between the brain and the intestines. Although researchers do not yet understand all of the links between changes in the nervous system and IBS, they point out the similarities between mild digestive upsets and IBS. Just as healthy people can feel nauseated or have an upset stomach when under stress, people with IBS react the same way, but to a greater degree. Finally, IBS symptoms sometimes intensify during menstruation, which suggests that female reproductive hormones are another trigger.


Diagnosing IBS is a fairly complex task because the disorder does not produce changes that can be identified during a physical examination or by laboratory tests. When IBS is suspected, the doctor (who can be either a family doctor or a specialist) needs to determine whether the patient's symptoms satisfy the Rome criteria. The doctor must rule out other conditions that resemble IBS, such as Crohn's disease and ulcerative colitis. These disorders are ruled out by questioning the patient about his or her physical and mental health (the medical history), performing a physical examination, and ordering laboratory tests. Normally the patient is asked to provide a stool sample that can be tested for blood and intestinal parasites. In some cases x rays or an internal examination of the colon using a flexible instrument inserted through the anus (a sigmoidoscope or colonoscope) is necessary. The doctor also may ask the patient to try a lactose-free diet for two or three weeks to see whether lactose intolerance is causing the symptoms.


Dietary changes, sometimes supplemented by drugs or psychotherapy, are considered the key to successful treatment. The following approach, offered by Dalton and Drossman, is typical of the advice found in the medical literature on IBS. The authors tie their approach to the severity of the patient's symptoms:

Mild symptoms

Dalton and Drossman recommend a low-fat, high-fiber diet. Problem-causing substances such as lactose, caffeine, beans, cabbage, cucumbers, broccoli, fatty foods, alcohol, and medications should be identified and avoided. Bran or 15-25 grams a day of an over-the-counter psyllium laxative (Metamucil or Fiberall) may also help both constipation and diarrhea. The patient can still have milk or milk products if lactose intolerance is not a problem. People with irregular bowel habits--particularly constipated patients--may be helped by establishing set times for meals and bathroom visits.

Moderate symptoms

The advice given by Dalton and Drossman in mild cases applies here as well. They also suggest that patients keep a diary of symptoms for two or three weeks, covering daily activities including meals, and emotional responses to events. The doctor can then review the diary with the patient to identify possible problem areas.

Although a high-fiber diet remains the standard treatment for constipated patients, such laxatives as lactulose (Chronulac) or sorbitol may be prescribed. Loperamide (Imodium) and cholestyramine (Questran) are suggested for diarrhea. Abdominal pain after meals can be reduced by taking antispasmodic drugs such as hyoscyamine (Anaspaz, Cystospaz, or Levsin) or dicyclomine (Bemote, Bentyl, or Di-Spaz) before eating.

Dalton and Drossman also suggest psychological counseling or behavioral therapy for some patients to reduce anxiety and to learn to cope with the pain and other symptoms of IBS. Relaxation therapy, hypnosis, biofeedback, and cognitive-behavioral therapy are examples of behavioral therapy.

Severe symptoms

When IBS produces constant pain that interferes with everyday life, antidepressant drugs can help by blocking pain transmission from the nervous system. Dalton and Drossman also underscore the importance of an ongoing and supportive doctor-patient relationship.

Alternative treatment

Alternative and mainstream approaches to IBS treatment overlap to a certain extent. Like mainstream doctors, alternative practitioners advise a high-fiber diet to reduce digestive system irritation. They also suggest avoiding alcohol, caffeine, and fatty, gassy, or spicy foods. Recommended stress management techniques include yoga, meditation, hypnosis, biofeedback, and reflexology. Reflexology is a technique of foot massage that is thought to relieve diarrhea, constipation, and other IBS symptoms.

Alternative medicine also emphasizes such herbal remedies as ginger (Zingiber officinale), buckthorn (Rhamnus purshiana), and enteric-coated peppermint oil. Enteric coating prevents digestion until the peppermint oil reaches the small intestine, thus avoiding irritation of the upper part of the digestive tract. Chamomile (Matricaria recutita), valerian (Valeriana officinalis), rosemary (Rosemarinus officinalis), lemon balm (Melissa officinalis), and other herbs are recommended for their antispasmodic properties. The list of alternative treatments for IBS is in fact quite long. It includes aromatherapy, homeopathy, hydrotherapy, juice therapy, acupuncture, chiropractic, osteopathy, naturopathic medicine, and Chinese traditional herbal medicine.


IBS is not a life-threatening condition. It does not cause intestinal bleeding or inflammation, nor does it cause other bowel diseases or cancer. Although IBS can last a lifetime, in up to 30% of cases the symptoms eventually disappear. Even if the symptoms cannot be eliminated, with appropriate treatment they can usually be brought under control to the point where IBS becomes merely an occasional inconvenience. Treatment requires a long-term commitment, however; six months or more may be needed before the patient notices substantial improvement.

Key Terms

The opening at the lower end of the rectum.
Crohn's disease
A disease characterized by inflammation of the intestines. Its early symptoms may resemble those of IBS.
Passage of feces through the anus.
Undigested food and other waste that is eliminated through the anus. Feces are also called fecal matter or stools.
A sugar found in milk and milk products. Some people are lactose intolerant, meaning they have trouble digesting lactose. Lactose intolerance can produce symptoms resembling those of IBS.
The periodic waves of muscular contractions that move food through the intestines during the process of digestion.
Ulcerative colitis
A disease that inflames and causes breaks (ulcers) in the colon and rectum, which are parts of the large intestine.

Further Reading

For Your Information


  • The Burton Goldberg Group. Alternative Medicine: The Definitive Guide. Puyallup, WA: Future Medicine Publishing, 1993.
  • Lynn, Richard B., and Lawrence S. Friedman. "Irritable Bowel Syndrome." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998.


  • Dalton, Christine B., and Douglas A. Drossman. "Diagnosis and Treatment of Irritable Bowel Syndrome." American Family Physician (February 1997): 875+.
  • Hendricks, Melissa. "Bowels in an Uproar." Johns Hopkins Magazine (April 1997). (1 May 1998).
  • "Irritable Bowel Syndrome: Treating the Mind to Treat the Body." Tufts University Health & Nutrition Letter (September 1997): 4+.
  • Maxwell, P. R., M. A. Mendall, and D. Kumar. "Irritable Bowel Syndrome." The Lancet 350(1997): 1691+.


  • International Foundation for Functional Gastrointestinal Disorders. PO Box 17864, Milwaukee, WI 53217. (888) 964-2001.
  • National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892-3570.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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