Clinical Presentation And Diagnosis Diagnosis

© The diagnosis of IBS is made by symptom-based criteria and the exclusion of organic disease. IBS is diagnosed by obtaining a careful and thorough history to identify symptoms characteristic of the disorder. It is equally important to distinguish among IBS and conditions having similar symptoms. Patients should be questioned about the character of their stools. This should include questions about frequency, consistency, color, and size. Moreover, because of the functional nature of IBS, a patient may present with symptoms of upper GI problems such as gastroesophageal reflux disease or with excessive flatulence. Patients should also be questioned about diet to determine whether symptoms seem to occur in relationship to meals or specifically after consumption of certain dietary products.

Barium enema, sigmoidoscopy, or colonoscopy may be indicated in the presence of red flag symptoms (fever, weight loss, bleeding, and anemia, which may be accompanied by persistent severe pain), which often point to a potentially serious non-IBS problem. A barium enema may identify polyps, diverticulosis, tumors, or other abnormalities that might be responsible for the symptoms. In addition, exaggerated haus-tral contractions may be noted with barium enema. Such contractions impede stool movement and contribute to constipation. Flexible sigmoidoscopy can be performed to identify obstruction in the rectum and lower colon, whereas colonoscopy can evaluate the entire colon for organic disease.

Clinical Presentation of IBS


• Patients report a history of abdominal pain or discomfort that is relieved with defecation. Symptom onset is associated with change in frequency or appearance of stool. Some persons experience hard, dry stools whereas others experience loose or watery stools. Some stools may be small and pellet-like in appearance while others may be narrow and pencil-like.

• Symptoms can typically be categorized as either IBS with diarrhea (IBS-D) or IBS with constipation (IBS-C). Patients with IBS-D usually report more than three loose or watery stools daily. Those with IBS-C usually have fewer than three bowel movements per week; stools are typically hard and lumpy and accompanied by straining. However, stool frequency may be normal in many cases. The Rome III diagnostic criteria (see Diagnosis) place more emphasis on stool form unlike Rome II, which emphasized frequency.

• While many patients fit into one of these subtypes, some patients report alternating episodes of diarrhea and constipation (irritable bowel syndrome with constipation and diarrhea [IBS-M], where M represents mixed).

• Other common symptoms include: (a) feelings of incomplete evacuation, (b) abdominal fullness, (c) bloating, (d) flatulence, (e) passage of clear or white mucus with a stool, and (f) occasional fecal incontinence.

• Periods of normal stools and bowel function are punctuated by episodes of sudden symptoms.

• Symptoms are often exacerbated by stress.

• Left lower quadrant abdominal pain is often brought on or made worse by eating. Passage of stool or flatus may provide some relief.

• IBS-C can often be distinguished from functional constipation primarily by the presence of abdominal pain and discomfort. Although pain and discomfort may be present in some patients with functional constipation, it is an expected feature of IBS.

• Patients with IBS may experience comorbidities outside the Gl tract such as fibromyalgia, sleep disturbances, headaches, dyspareunia, and temporomandibular joint syndrome.


• The physical examination is often normal in IBS.

• The patient may appear to be anxious.

• Palpation of the abdomen may reveal left lower quadrant tenderness, which may indicate a tender sigmoid colon.

• Abdominal distention may be present in some cases.

• The following "red flag" or alarm features are not associated with IBS and may indicate inflammatory bowel disease, cancer, or other disorders: fever, weight loss, bleeding, and anemia, which may be accompanied by persistent severe pain.

Laboratory Tests

• In most cases, laboratory testing reveals no abnormalities in IBS, but certain tests can be used to identify other causes for the patient's symptoms.

• CBC may identify anemia, which may suggest blood loss and an organic source for Gl symptoms.

• Serum electrolytes and chemistries may indicate metabolic causes of symptoms.

• Thyroid-stimulating hormone (TSH) should be ordered when thyroid dysfunction is suspected. Hypothyroidism may be responsible for constipation and related symptoms.

• Stool testing for ova and parasites may identify C. difficile and amoebae as possible causes of diarrhea rather than IBS.

• Fecal leukocytes can be found in inflammatory diarrhea, especially when due to invasive microorganisms.

• A positive stool guaiac test indicating blood in the Gl tract does not support a diagnosis of IBS.

• An elevated erythrocyte sedimentation rate is consistent with a systemic inflammatory process such as inflammatory bowel disease rather than IBS.

• Testing for lactase deficiency can confirm the presence of lactose intolerance, which may explain the symptoms.

IBS diagnosis has long been symptom based. Manning defined the first widely used practical criteria: (a) abdominal pain relieved by defecation with either (i) looser stools with pain onset, or (ii) frequent stools with pain onset; (b) abdominal disten-

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tion; (c) mucus in the stool; and (d) sensation of incomplete evacuation. '

The Rome III criteria are the most current diagnostic criteria and can also be applied clinically.19 They presume the absence of a structural or biochemical explanation for the symptoms. The Rome III criteria define IBS as occurring when symptoms of recurrent abdominal pain or discomfort exist for at least 3 days/month in the last 3 months associated with two or more of the following: (a) improvement with defecation, (b) onset associated with a change in the frequency of stool, and/or (c) onset associated with a change in the form (appearance) of stool. These criteria should be fulfilled for the previous 3 months with symptom onset at least 6 months prior to diagnosis. IBS is unlikely if symptom onset occurs in old age, the disorder has a steady but aggressive course, or the patient experiences frequent awakening because of symptoms.

Patient Encounter 3, Part 1

A 38-year-old woman presents complaining of headache, abdominal pain, bloating, occasional nausea, and excessive belching. These symptoms have occurred with increasing frequency over the past 2 to 3 weeks. She has missed 2 days of work recently. The abdominal pain is crampy in character and located in the left lower abdominal area. She has also had alternating episodes of loose stools and hard dry stools and the presence of white thread-like material in her stool during some of the past 3 weeks. She reports no family history of Gl problems.

Which of the patient S symptoms are characteristics of IBS?

How well does this woman fit the typical epidemiologic profile of patients with IBS?

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