Review article: abdominal bloating and distension in functional gastrointestinal disorders--epidemiology and exploration of possible mechanisms.

BACKGROUND A sensation of abdominal bloating, sometimes accompanied by an increase in girth (distension), is one of the most common and most intrusive features of functional bowel disorders. AIM To conduct a systematic, evidence-based review of the epidemiology and pathophysiology of abdominal bloating and its relationship to distension. METHODS The terms bloating, distension, functional bowel, irritable bowel syndrome, constipation and diarrhoea were searched on MEDLINE up to 2006. References from selected articles and relevant abstracts were also included. RESULTS Approximately 50% of irritable bowel syndrome patients with bloating also experience an increase in abdominal girth and this is more pronounced with constipation than diarrhoea. Bloating appears to be more frequently associated with visceral hypersensitivity, whereas distension is more often related to hyposensitivity and delayed transit. Although there is little evidence for excessive gas as a cause of bloating, gas infusion studies suggest that handling of gas may be impaired in irritable bowel syndrome and there may also be abnormal relaxation of the anterior abdominal musculature in these patients. CONCLUSIONS There is unlikely to be a single cause for bloating and distension, which probably have different, but overlapping, pathophysiological mechanisms. Relieving constipation might help distension, but the treatment of bloating may need more complex approaches involving sensory modulation.