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Pathophysiology of irritable bowel syndrome

Author
Arnold Wald, MD
Section Editor
Nicholas J Talley, MD, PhD
Deputy Editor
Shilpa Grover, MD, MPH

INTRODUCTION

Irritable bowel syndrome (IBS) is a gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits in the absence of any organic cause. It is the most commonly diagnosed gastrointestinal condition and accounts for approximately 30 percent of all referrals to gastroenterologists [1]. The pathophysiology of IBS remains uncertain [2]. It is viewed as a disorder resulting from an interaction among a number of factors. Despite multiple investigations, data have been conflicting and no abnormality has been found to be specific for this disorder.

The traditional focus has been on alterations in gastrointestinal motility and on visceral hypersensitivity. More recent studies have considered the role of inflammation, alterations in fecal flora, and bacterial overgrowth. Also being considered is the role of food sensitivity. Whether a genetic predisposition exists is also being investigated.

This topic will review the multiple factors that have been considered to play a role in the pathophysiology of IBS. The clinical manifestations, diagnosis, and therapy of this disorder are discussed separately. (See "Clinical manifestations and diagnosis of irritable bowel syndrome in adults" and "Treatment of irritable bowel syndrome in adults".)

GASTROINTESTINAL MOTILITY

Although the symptoms of irritable bowel syndrome (IBS) have focused attention on colonic motility, no predominant pattern of motor activity has emerged as a marker for IBS. However, motor abnormalities of the gastrointestinal tract (GI) are detectable in some patients with IBS. Abnormalities observed include increased frequency and irregularity of luminal contractions [3-5], prolonged transit time in constipation-predominant IBS [6], and an exaggerated motor response to cholecystokinin and meal ingestion in diarrhea-predominant IBS [7]. The relevance of these motor function alterations to symptoms has yet to be established. However, pharmacologic stimulation of gut motility in IBS patients has been reported to reduce gas retention and improve symptoms, suggesting that a motility disturbance underlies this complaint in some patients [8].

VISCERAL HYPERSENSITIVITY

Visceral hypersensitivity (increased sensation in response to stimuli) is a frequent finding in irritable bowel syndrome (IBS) patients. Perception in the gastrointestinal (GI) tract results from stimulation of various receptors in the gut wall. These receptors transmit signals via afferent neural pathways to the dorsal horn of the spinal cord and ultimately to the brain.

                

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Literature review current through: Nov 2016. | This topic last updated: Thu Aug 11 00:00:00 GMT 2016.
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