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Irritable Bowel Syndrome

Synonyms of Irritable Bowel Syndrome

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

Disorder Subdivisions

  • No subdivisions found.

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.

Related Disorders

Symptoms of the following disorders can be similar to those of Irritable Bowel Syndrome. Comparisons may be useful for a differential diagnosis:

Ulcerative Colitis is an acute inflammatory bowel disease characterized by diarrhea and blood in the stools because of multiple, irregular ulcerations of the bowel. The initial symptoms of this disorder may include a general feeling of weakness (malaise) and fatigue. There may be abdominal discomfort, along with a change in the frequency and consistency of stools. Other symptoms may include abdominal pain, cramping, and urgency (tenesmus). Weight loss and a decrease in appetite are also associated with Ulcerative Colitis. (For more information on this disorder, choose "Ulcerative Colitis" as your search term in the Rare Disease Database.)

Crohn's Disease is an inflammatory bowel disease characterized by severe, chronic inflammation of the intestinal wall or any portion of the gastrointestinal tract. Symptoms may include nausea, vomiting, fever, night sweats, loss of appetite, a general feeling of weakness, waves of abdominal pain and discomfort, diarrhea, and/or bleeding from the rectum. These symptoms can be difficult to manage and diagnosis is frequently delayed. (For more information on this disorder, choose "Crohn's" as your search term in the Rare Disease Database.)

Primary Sclerosing Cholangitis is a rare collagen disorder involving inflammation and blockage of the bile duct, liver ducts, and gallbladder. Symptoms of this disorder include abdominal pain, loss of appetite, nausea, vomiting, and/or weight loss. Later symptoms may include a yellow discoloration to the skin (jaundice), fever, chills, and/or itching of the skin. Bacterial infections resulting from Ulcerative Colitis, Crohn's Disease, and/or Vasculitis may be associated with bile duct blockages in Primary Sclerosing Cholangitis. (For more information on this disorder, choose "Primary Sclerosing Cholangitis" as your search term in the Rare Disease Database.)

Chronic Erosive Gastritis is an inflammatory disorder characterized by multiple lesions in the mucus lining of the stomach. Symptoms of this disorder may include a burning or heavy feeling in the stomach, mild nausea, vomiting, loss of appetite and general weakness. In severe cases of Chronic Erosive Gastritis there may be bleeding from the stomach that may lead to anemia. (For more information on this disorder, choose "Chronic Erosive Gastritis" as your search term in the Rare Disease Database.)

Glucose-Galactose Malabsorption (carbohydrate intolerance) is a rare inherited disorder characterized by the inability of the small intestine to transport and absorb glucose and galactose. The symptoms of this disorder in children may include diarrhea, dehydration, and failure to gain weight. In adults, symptoms of this disorder may include bloating, nausea, diarrhea, abdominal cramps, rumbling sounds caused by gas in the intestine (borborygmi), and/or excessive urination. (For more information on this disorder, choose "Glucose-Galactose Malabsorption" as your search term in the Rare Disease Database.)

Diverticulitis is a common digestive disorder characterized by inflammation of one or more of the sacs (diverticula) that can form due to protrusion of the inner lining of the colon through the intestinal wall. Symptoms of this disorder may include pain in the lower abdomen, pain when urinating, constipation, diarrhea, fever and/or rectal bleeding. (For more information on this disorder, choose "Diverticulitis" as your search term in the Rare Disease Database.)

Giardiasis is a rare gastrointestinal disorder characterized by infection of the intestines caused by the single-celled organism Giardia lamblia. Symptoms of this disorder may include crampy abdominal discomfort, watery diarrhea, gas pains, and foul-smelling stools. Acute attacks usually last for 3 or 4 days. People with chronic Giardiasis may experience weight loss, a profound loss of appetite, nausea, vomiting, and/or chronic diarrhea. (For more information on this disorder, choose "Giardiasis" as your search term in the Rare Disease Database.)

Amebiasis is a rare gastrointestinal disorder characterized by infection of the intestines by a single-celled organism Entamoeba histolytica. Frequently this disorder may initially have no symptoms but some people experience episodes of diarrhea and constipation, gas pains, and/or abdominal cramps.

Lactose Intolerance is a malabsorption syndrome in which a deficiency of the intestinal enzyme lactase causes impaired absorption of nutrients from the small bowel. Symptoms in children include diarrhea and failure to thrive. Adult symptoms may include rumbling noises in the intestines, bloating, and excessive gas. Abdominal cramps and diarrhea may also be present. (For more information on this disorder, choose "Lactose Intolerance" as your search term in the Rare Disease Database.)

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:

Irritable Bowel Syndrome Resources



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The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Report last updated: 2008/05/04 00:00:00 GMT+0

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