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Irritable bowel syndrome and functional bowel disorders 

Irritable bowel syndrome and functional bowel disorders

Irritable bowel syndrome and functional bowel disorders

D.G. Thompson


November 26, 2012: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

A relevant case history from Oxford Case Histories in Gastroenterology and Hepatology has been added to this chapter.

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date: 28 April 2017

Symptoms suggestive of disturbed lower gastrointestinal function without adequate explanation are very common in adults in the Western world, up to 15% of whom experience such symptoms at any one time, although most do not seek medical advice. It is not clear whether the symptoms of those individuals who do seek medical help have a different pathophysiological basis from those who do not, and whether the seeking of medical advice is more an indication of a worried individual than of disturbed gut function.

The currently used terms are best viewed as an attempt to provide some clinically useful rather than pathophysiologically accurate categorization of patients and their symptoms. The ‘Rome criteria’ recognize (1) irritable bowel syndrome, characterized by abdominal pain that is relieved by defecation with associated change in frequency in defecation and/or stool consistency; (2) functional bloating; (3) functional constipation; (4) functional diarrhoea; and (5) functional abdominal pain.

Routine haematological and biochemical screening is usually done on the assumption that they will be normal. Features that raise the suspicion of organic disease and indicate a need for further investigation include the onset of symptoms in middle-aged or older individuals, weight loss, or blood in the stool.

Management remains empirical: no single pharmacological agent or group of agents has ever been found to be consistently effective. The principal task of the physician is to give explanation and reassurance (sometimes supplemented by psychological treatments), but particular symptoms are often treated as follows: (1) constipation—defecation may be eased by supplementary dietary fibre and poorly absorbed fermentable carbohydrates which increase faecal bulk and soften the stool; osmotic laxatives and enemas are used for the severely constipated patient with slow transit; (2) diarrhoea—attention to diet is often helpful, as are simple antidiarrhoeal agents; (3) abdominal pain—antispasmodics (e.g. hyoscine butyl bromide) are frequently employed, as are low doses of antidepressants.

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