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Irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a disorder of the intestines that causes abdominal discomfort or pain and altered bowel habits (diarrhea and/or constipation).

Symptoms occur because nerves in the gut or central nervous system are too sensitive to painful stimuli. The intestinal muscle may also contract too strongly. There is no evidence of infection, inflammation, cancer, or damage to the intestines and there is no increased risk for developing such problems in the future. Therefore, intestinal bleeding or symptoms of infection (such as fever) cannot be attributed to IBS, and should be investigated to rule out a another existing disease.

Symptoms of IBS include the following:

  • Abdominal discomfort or pain;
  • Gassiness and bloating;
  • Changes in bowel habits (constipation, diarrhea).


Research has shown that the following factors contribute to the development of IBS symptoms:

  • Increased sensitivity of sensory nerves to stimuli;
  • Abnormal contractions of intestinal muscle;
  • Genetic factors;
  • Low-grade inflammation;
  • Infectious gastroenteritis that resolves (the infection is cleared by the body) but results in IBS;
  • Changes in the intestinal micro-organisms;
  • Hormonal factors;
  • Food sensitivities;
  • Emotional stress.


The gastroenterologist performs a thorough history and physical examination before conducting certain tests and, if necessary, endoscopic and imaging studies. Symptoms must be present for at least 3 months for IBS to be considered a possible diagnosis. Diagnostic tests may include:

  • Blood tests: To rule out anemia, inflammation and celiac disease;
  • Stool tests: To rule out bacteria causing diarrhea;
  • Colonoscopy: To rule out inflammatory bowel disease and colon cancer;
  • CT of the abdomen and pelvis: To rule out other causes of abdominal pain.


  • Understanding the mechanisms of IBS, including the role of stress, diet and (in women) menstrual cycle
  • Diet changes: Reducing or eliminating foods that causes symptoms. A low FODMAP diet limits foods that are high in fructose, lactose, fructans, galactans (complex carbohydrate, chains of the sugar galactose) and polyols (sugar alcohols).
  • Medications:   
    • Fiber supplements to bulk up stool in patients with diarrhea;
    • Anti-diarrheals (such as loperamide) in patients with diarrhea;
    • Laxatives (such as milk of magnesia and polyethylene glycol) in patients with constipation;
    • Antispasmodics (such hyoscyamine and dicyclomine) to reduce intestinal spasms;
    • Antidepressants (such as nortriptyline) used to reduce the sensitivity of sensory nerves, and therefore decrease abdominal pain;
    • Lubiprostone, which increases intestinal fluid secretion and is approved for the treatment of irritable bowel syndrome with constipation in women 18 years and older.

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