Irritable Bowel Syndrome

National Organization for Rare Disorders, Inc.

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It is possible that the main title of the report Irritable Bowel Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • Adaptive Colitis
  • Colonic Neurosis
  • IBS
  • Irritable Colon Syndrome
  • Mucous Colitis
  • Spastic Colon
  • Unstable Colon

Disorder Subdivisions

  • None

General Discussion

Irritable Bowel Syndrome, also known as Spastic Colon or Mucous Colitis, is a digestive disorder characterized by an abnormal increase in the mobility of the intestines (small and large). Symptoms may include abdominal pain, constipation, and diarrhea. This disorder is common; about 50 percent of all gastrointestinal problems are associated with Irritable Bowel Syndrome. There is no organic disease present, only the function of the intestines is affected. However, based on the symptoms, this disease can be confused with other organic bowel diseases.


Symptoms of the Irritable Bowel Syndrome include abdominal discomfort, an increase or decrease in the frequency of bowel movements, and abnormally loose or hard stools. Other symptoms may include a sensation of abdominal bloating, nausea, headache, and/or fatigue. Uncomfortable abdominal sensations are caused by excessive amounts of intestinal gas.

Irritable Bowel Syndrome is divided into two different types based on symptoms. The Spastic Colon type of this disorder is characterized by bowel movements accompanied by abdominal pain, and episodes of constipation or diarrhea. Some patients experience alternating episodes of both. People with Spastic Colon typically experience lower abdominal pain (sigmoid colon) that may be colicky or dull and continuous; symptoms may become worse during or after eating. Fatigue, depression, and/or anxiety may also occur.

Painless Diarrhea is the other type of Irritable Bowel Syndrome. It is characterized by urgent diarrhea which occurs immediately upon awakening or immediately after eating. The involuntary loss of stools (fecal incontinence) may occur in some patients. Nighttime diarrhea is uncommon in people with Irritable Bowel Syndrome.


Irritable Bowel Syndrome is not caused by a structural (anatomic) defect in the intestines nor organic disease. Attacks of the disorder may coincide with periods of emotional stress. Individuals with Irritable Bowel Syndrome may have a heightened sensitivity to increased intestinal motility that may be triggered by certain drugs, foods, or hormones. Abdominal pain may increase after eating, especially those foods with high fat content.

It has been suggested that many affected individuals initially experience symptoms of irritable bowel syndrome after they have a bout with an infectious disease known as bacterial gastroenteritis (e.g., salmonella, etc.). During the year following gastroenteritis, development of irritable bowel syndrome has been demonstrated to be more than 10 times higher than normal. Scientists do not know why this occurs.

Affected Populations

Irritable Bowel Syndrome is a very prevalent digestive disorder that accounts for approximately 50% of all gastrointestinal illnesses referred to physicians. This disorder affects women about three times more often than men. It occurs with greater frequency in women between the ages of 15 and 45 years of age. The symptoms of Irritable Bowel Syndrome may occur in up to 25 percent of the general population. Many individuals do not seek medical attention.

Standard Therapies


The diagnosis of Irritable Bowel Syndrome is made by the exclusion of other organic bowel diseases that have similar symptoms. The age of the individual and the severity of the symptoms determine the diagnostic tests to be performed. Affected individuals over the age of 40 years generally require more rigorous testing to eliminate other more serious conditions.

People with Irritable Bowel Syndrome need to be reassured there is no other, more serious organic disease. Regular physical activity may help to relieve anxiety and is important in helping bowel function. Generally a normal diet can be followed. Foods that may cause excessive gas, such as those containing fermentable carbohydrates (e.g., beans, cabbage) or other foods that may aggravate symptoms should be eliminated from the diet if possible. Laxatives should also be avoided if possible. Those who experience spastic constipation associated with this disorder may find the use of unprocessed bran helpful. Metamucil (Psyllium hydrophilic mucilloid) taken with water may help to stabilize the water content of the bowel.

For some affected individuals, certain medications may be prescribed, such as anticholinergic agents (i.e., propantheline), mild tranquilizers (i.e., chlordiazepoxide), or sedatives. Tranquilizers may act to block a stress-induced increase in intestinal motility. Particular agents may also be prescribed to relieve diarrhea, such as the antidiarrheal drug loperamide. Loperamide may also be an effective treatment for episodes of diarrhea in people with alternating constipation and diarrhea.

The U.S. Food and Drug Administration (FDA) has approved Zelnorm, made by Novartis Pharmaceuticals Corporation of East Hanover, New Jersey, for short-term use by women with irritable bowel syndrome whose primary symptom is constipation. The safety and effectiveness of Zelnorm in men have not been established.

The FDA also has reapproved Lotronex made by GlaxoSmithKline for the form of irritable bowel syndrome characterized by diarrhea. The drug was originally approved by the FDA in February 2000 but later withdrawn from the market because of safety concerns. However, appeals from patients led the FDA to allow Lotronex back on the market in June 2002 but only for the most serious cases of IBS and with a special risk-management distribution program.

On April 29, 2008, the Food and Drug Administration (FDA) approved Amitiza (lubiprostone) for the treatment of Irritable Bowel Syndrome with Constipation (IBS-C) in adult women aged 18 and over. With this approval, Amitiza becomes the only FDA-approved medical treatment for IBS-C available in the United States.

As a treatment for IBS-C, Amitiza should be taken twice a day in 8 microgram doses with food and water. Patients and their health care professionals should periodically assess the need for continued therapy.

Amitiza is manufactured by Sucampo Pharmaceuticals, Bethesda, Md., and Takeda Pharmaceuticals America, Inc., Deerfield, Ill.

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010


For information about clinical trials sponsored by private sources, contact:



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