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Patients often complain of intermittent abdominal pain accompanied by diarrhea or constipation or both of years’ duration. The diarrhea is often accompanied by cramps that are relieved with defecation. Pain cannot be explained by structural or biochemical abnormalities. Weight loss or anemia should alert the clinician to other possibilities.

image New persistent changes in bowel habits (either diarrhea or constipation) should be thoroughly evaluated to exclude colon cancer, IBD, or another process. An assumption of IBS in such patients is inappropriate.


  1. Affects 8.9% of men and 14% of women.

  2. Etiology is a combination of altered motility, visceral hypersensitivity, autonomic dysfunction, and psychological factors.

  3. Symptoms are often exacerbated by psychological or physical stressors.

  4. Patients may have pain associated primarily with diarrhea (IBS-D), constipation (IBS-C) or a mixed bowel pattern (IBS-M).


  1. There are no known biochemical or structural markers for IBS.

  2. A variety of symptoms are common in patients with IBS including lower abdominal pain, passage of mucous, feeling of incomplete evacuation, loose or frequent stools at onset of pain, and pain relieved by defecation. However, none of these are very predictive (LR+, 1.3–2.1; LR–, 0.59–0.88).

  3. Only abdominal pain is very sensitive (sensitivity, 90%; specificity, 32%) and is also required by the criteria.

  4. Diarrhea pattern

    1. One study suggested that patients with diarrhea-predominant IBS were more likely to have irregularly irregular diarrhea that fluctuated over days whereas patients with inflammatory diseases (IBD and celiac disease) were more likely to have persistent diarrhea that fluctuates over months.

    2. Persistent diarrhea increased the likelihood of IBD (LR+, 4.2).

    3. A more extensive work-up may be indicated in patients with persistent, constant diarrhea.

  5. The diagnosis is usually made by a combination of (1) a consistent history, (2) the absence of alarm features, and (3) a limited work-up to exclude other diseases.

    1. Consistent history

      1. Although a variety of criteria have been developed (ie, Rome criteria), a recent review by the American College of Gastroenterology suggested a consistent history was abdominal pain or discomfort that occurs in association with altered bowel habits for at least 3 months.

      2. Patients may also report a relief of pain with defecation.

    2. Alarm symptoms (suggest alternative diagnosis and necessitate evaluation)

      1. Positive fecal occult blood test or rectal bleeding

      2. Anemia

      3. Unintentional and unexplained weight loss

      4. Fever

      5. Family history of colorectal cancer, IBD, or celiac disease

      6. Recent antibiotic use

    3. Limited work-up

      1. A CBC is appropriate to rule out anemia, which would suggest alternative diagnoses, and CRP to rule out inflammatory diseases.

      2. Other diagnostic testing is not recommended for young patients without alarm features, with the exception of serologic testing for celiac disease in patients with IBS-D.

        1. Although recommended by the American College of Gastroenterology, one study found the incidence of confirmed celiac disease in IBS-D patients (without alarm features) to be very low (0.41%) and not different from asymptomatic patients.

        2. May best be reserved for ...

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