Irritable bowel syndrome

Published on 08/04/2015 by admin

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Last modified 08/04/2015

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Chapter 9 IRRITABLE BOWEL SYNDROME

DEFINITIONS AND CATEGORIES

In less than 50% of patients with chronic or relapsing symptoms such as abdominal pain or discomfort, structural or biochemical abnormalities can be found that explain these symptoms. On the other hand, even if there are structural abnormalities, such as diverticula in the sigmoid colon, these abnormalities may not explain the symptoms in patients presenting for assessment. If there are no abnormalities explaining symptoms, a functional gastrointestinal disorder can be diagnosed.

If there is no structural abnormality to explain the symptoms, and symptoms such as pain or discomfort are associated with changes in bowel habit, irritable bowel syndrome (IBS) can be diagnosed. The most stringent definitions for functional gastrointestinal disorders have been provided by the Rome Committee, an international working party. The Rome III criteria for IBS are summarised in Table 9.1. Essentially, IBS can be diagnosed when structural lesions are absent (or unlikely based upon the clinical presentation) and the patient suffers from chronic or relapsing abdominal discomfort or pain associated with an abnormality of bowel movements (constipation, diarrhoea or alternating diarrhoea and constipation). Bloating is also common.

TABLE 9.1 Diagnostic criteria for irritable bowel syndrome (Rome III)

Recurrent abdominal pain or discomfort for at least 3 months, and symptoms at least 3 days/month associated with two or more of the following:

Based upon the symptoms, patients with IBS are usually categorised into one of three groups: IBS with predominant diarrhoea (IBS-D) or predominant constipation (IBS-C) or a mixed pattern of diarrhoea and constipation. Alternating refers to changing from diarrhoea to a constipation pattern (IBS-A). There is a group of patients who develop IBS symptoms after an episode of acute infectious diarrhoea, sometimes accompanied by fever, nausea and vomiting. This syndrome is now labelled post-infectious or PI-IBS. Interestingly, post-infectious IBS is usually associated with diarrhoea predominant IBS. Chronic abdominal pain or discomfort in the absence of abnormalities in stool pattern is not IBS, but is called chronic functional abdominal pain.

PATHOPHYSIOLOGY OF IBS

A number of mechanisms are believed to be involved in the manifestation of IBS. Indeed, there is evidence accumulating that IBS is not one disease, but most likely represents a group of disorders with different pathophysiologies.

MANAGEMENT

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