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Irritable bowel syndrome 

Irritable bowel syndrome
Chapter:
Irritable bowel syndrome
Author(s):

Adam D. Farmer

, and Qasim Aziz

DOI:
10.1093/med/9780198746690.003.0308
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date: 03 March 2021

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. 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 based on disordered gut–brain interactions. Irritable bowel syndrome is defined according to the Rome III criteria as recurrent abdominal pain or discomfort associated with a change in bowel habit for at least 6 months, with symptoms experienced on at least 3 days of at least 3 months. Many subtypes are recognized. Routine haematological and biochemical screening is usually performed on the assumption that it 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 provide 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, as well as more novel agents; (2) diarrhoea—attention to diet is often helpful, as are simple antidiarrhoeal agents; and (3) abdominal pain—antispasmodics (e.g. hyoscine butyl bromide) are frequently used, as are antidepressants.

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