Table of Contents


and the reason for this is unknown. IBS is also called spastic colon.


Irritable bowel syndrome is not a life-threatening disorder and does not progress to any more serious conditions, but it is the cause of about one of every 10 doctor visits in the United States. Its symptoms, although not medically serious, are varied, changeable, and intrusive enough to impact an individual’s quality of life. IBS causes people to miss school or work, avoid certain activities, and it interferes with personal relationships.

IBS involves both the large intestine (colon) and the small intestine. It is best described as a disorder in which the all tests show that the bowel is structurally normal—no infection, no tumors or polyps, no abnormalities in the cells lining of the intestinal wall. It is not contagious, and it is not strictly inherited, yet the individual with IBD has pain, cramping, and either.


Idiopathic—Occurring from unknown causes.

Neurotransmitter—One of a group of chemicals secreted by a nerve cell (neuron) to carry a chemical message to another nerve cell, often as a way of transmitting a nerve impulse. Examples of neuro-transmitters include acetylcholine, dopamine, serotonin, and norepinephrine.

Rectum—The last few inches of the large intestine.

constipation, diarrhea, or alternating periods of both, so something is clearly wrong.

IBS should not to be confused with inflammatory bowel disease (IBD). Inflammatory bowel diseases such as Crohn’s disease, ulcerative colitis, and celiac disease cause changes in the cells lining the wall of the intestine. These cell abnormalities can be seen in samples (biopsies) taken from the wall of the intestine. In a person who has IBD, the cells in samples taken from the lining of the intestine look normal. Inflammatory bowel diseases increase the risk of developing intestinal cancers; IBS does not.


As many as one out of every five Americans has symptoms of irritable bowel syndrome. The disorder appears to be most common in Western countries. However poor access to medical care, different cultural attitudes toward illness, and the fact that the disorder is neither life threatening nor contagious and does not have to be reported to any central authority makes it difficult to tell what the actual rates are in developing countries. In Western countries estimates of the number of people with IBD range from 9–23% of the population.

IBS occurs in both children and adults. About 14% of high school students and 6% of middle school students report IBD symptoms. In these groups, IBS accounts for 4–5% of all absences from school. In about half of all people who have the disorder, symptoms begin before age 35; 30% say that their symptoms began in childhood. Most other people with IBS develop symptoms between ages 35 and 50. Women are two to three times more likely to have IBS than men.

Causes and symptoms

Whatever the cause, symptoms of IBS include pain or discomfort in the abdomen, feeling bloated or having a lot of gas, diarrhea, constipation, or alternating periods of both, and mucus in the stool. The symptoms come and go and can change in a single individual over time. The impact of symptoms can range from mild to severe, and the intensity of symptoms can also change over time. Symptoms are usually reduced or relieved by a bowel movement.

Although they are not the cause of IBS, certain things can trigger symptoms. Triggers vary from person to person.

  • Food. Different foods are triggers for different people. Some common trigger foods are dairy products, sorbitol (a sweetener used in sugar-free products), foods containing caffeine, chocolate, and alcohol
  • Stress. Stress from any source often triggers or worsens symptoms in people with IBS
  • Illness. Other gastrointestinal illnesses caused by bacteria or viruses can trigger symptoms
  • Menstruation. Women seem to have more severe symptoms when they are menstruating, suggesting that changing hormone levels may affect symptoms


There are no tests for IBS. As a result, there are two different ways to arrive at a diagnosis of IBS. One is to perform tests to specifically eliminate other disorders with similar symptoms, such as ulcerative colitis. When other possible disease have been eliminated, then IBS is diagnosed.

The other approach to diagnosis is to use what is known as the Rome criteria for diagnosis. Following the Rome criteria, IBS is diagnosed if the symptoms of abdominal pain, diarrhea and/or constipation are present for at least 12 weeks (the weeks do not have to be consecutive) and several of the following conditions are met:

  • A change in the frequency of bowel movements
  • A change in the consistency of the stool
  • Straining to empty the bowels or a feeling or urgency to empty the bowels
  • Frequently feeling that the bowel is not completely empty
  • Mucus in the stool
  • Bloating
  • Symptoms are reduced by having a bowel movement

Note that blood in the stool, vomiting, fever, and diarrhea that awakens a person at night are not symptoms of IBS. Individuals with these symptoms should see a doctor promptly.

Often these two approaches to diagnosis are combined, and the physician may initially perform a sigmoidoscopy or a colonoscopy to look at the inside of the bowel. In these procedures, a tube called an endoscope is inserted through the rectum and into the colon. At the end of the endoscope is a tiny camera that allows the doctor to see if there is damage to the cells lining digestive tract. During this procedure, the doctor also removes small tissue samples (biopsies) in order to look for abnormal cells under the microscope. This can eliminate inflammatory bowel syndrome as the cause of symptoms.

The doctor may also do a lactose intolerance test. Lactose is a sugar found in milk. People who lack the enzyme to break down this sugar have symptoms similar to those of irritable bowel syndrome. Lactose intolerance is common, and a lactose intolerance test can confirm or eliminate lactose as the source of the symptoms.

The doctor may also do a blood test to determine if symptoms are caused by early or mild celiac disease. People with celiac disease are sensitive to gluten, a protein found in wheat, barley, rye, and the products made from these grains. Eating foods containing gluten often causes symptoms similar to IBS in people with celiac disease.


Because no functional problems can be found in people with IBS, family members and even some healthcare providers may be inclined to dismiss symptoms as caused by emotional problems or similar psychological upsets. However, the disease is real and not something that the patient can control. Finding a doctor with whom the patient can establish good communication and feel comfortable is an important first step in treatment.

Treatment of IBS is aimed at relieving symptoms and falls into three categories, lifestyle adjustments, learning new coping skills, and drug therapy. Lifestyle adjustments are include:

  • increasing fiber in the diet (see irritable bowel syndrome diet entry)
  • keeping a food diary to learn which foods are trigger foods and then avoiding them
  • drinking at least 6 glasses of water daily to help prevent constipation
  • getting regular exercise
  • eating meals at regular times; not skipping meals

Learning new coping skills may involve psychotherapy (talk therapy) or professional counseling to help resolve problems that are causing stress or learning techniques to cope with stress. Some of these coping techniques include biofeedback techniques to reduce stress, yoga, massage, meditation, deep breathing exercises, progressive relaxation exercises, and hypnosis.

Drug therapy depends on specific symptoms. Over the counter anti-diarrheal products such as loperamide (Imodium) can give the individual better bowel and reduce the impact of IBS on daily activities. Over the counter laxatives can be helpful to treat constipation but they must be used sparingly because regular use creates bowel dependence.

Bulk-forming or fiber supplement laxatives are generally the safest type of laxative. Some common brand names of fiber-supplement laxatives are Meta-mucil, Citrocel, Fiberall, Konsyl, and Serutan. These must be taken with water. They provide extra fiber that absorbs water and helps keep the stool soft. The extra bulk also helps move materials through the colon.

Stool softeners help prevent the stool from drying out. They are recommended for people who should not strain to have a bowel movement, for example, people recovering from abdominal surgeries or childbirth. Brand names include Colace and Surfak.

Stimulant laxatives such as Ducolax, Senokot, Correctol, and Purge increase the rhythmic contractions of the colon and move the material along faster.

Lubricants add grease to the stool so that it moves more easily through the colon. Mineral oil is the most common lubricant.

Saline laxatives such as Milk of Magnesia draw water from the body into the colon to help soften and move the stool.

As of April 2007, the only prescription drug to treat IBS is alosetron (Lotronex). In the United States, this drug was temporarily withdrawn from the market because of serious side effects including four deaths, but was reapproved with limitations. The drug can only be prescribed by doctors enrolled in a special program, and should only be used for cases of severe diarrhea-type IBS that has failed to respond to all other treatments. This drug is only approved for use in women. Tegaserod (Zelnorm), previously prescribed for severe constipation, was withdrawn from the American market at the request of the Food and Drug Administration in March 2007 because of serious heart-related side effects.

Some people with IBS have seen their symptoms improve when treated with low levels of tri-cyclic anti-depressants that affect serotonin levels in the brain. The dosage of these drugs is lower than that used to treat depression. Serotonin is a neurotransmitter that some researchers think play a role in IBS Newer selective serotonin reuptake inhibitor (SSRI) antidepressants seem to be less effective. People whose symptoms do no improve with lifestyle changes may want to talk to their doctor about this and also seek treatment for any depression or anxiety that accompanies the disorder.

Nutrition/Dietetic concerns

The main dietary concern of people with constipation-type IBS is increasing the amount of fiber in their diet. Insoluble fiber helps material move through the large intestine faster so that less water is reab-sorbed by the body and the stool remains softer. Soluble fiber dissolves in water and forms a gel that keeps the stool soft. Good sources of fiber include apples with skin, dried beans, pears with skin, brown rice, oatmeal, and popcorn.


Every year the symptoms of about 10% of people with IBD spontaneously disappear. The reason for this is not understood. For most people, however, IBS is a chronic disorder. Symptoms are erratic and changeable; there are periods of symptoms improve and periods when symptoms worsen. IBD is not a symptom of any other disorder, and it does not develop into any other more serious disease such as inflammatory bowel disorder or colon cancer.


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American College of Gastroenterology. P.O. Box 342260 Bethesda, MD 20827-2260. Telephone: (301) 263-9000. Website: <>.

American Gastroenterological Association. 4930 Del Ray Avenue, Bethesda, MD 20814. Telephone: (301) 654-2055. Fax: (301) 654-5920. Website: <>.

IBS Self Help and Support Group 1440 Whalley Avenue, ndash145, New Haven, CT 06515. Website: <>.

International Foundation for Functional Gastrointestinal Disorders. P. O. Box 170864, Milwaukee, WI 53217, Telephone: (888) 964-2001. Fax: (414) 964-7176. Website: <>.

National Digestive Diseases Information Clearinghouse (NDDIC). 2 Information Way Bethesda, MD 20892-3570. Telephone: (800) 891-5389. Fax: (703) 738-4929. Website: <>.


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Tish Davidson, A.M.