Tremolaterra F et al. (2006) Impaired viscerosomatic reflexes and abdominal-wall dystony associated with bloating. Gastroenterology 130: 1062–1068

A team of Spanish investigators has conducted a prospective, controlled study of abdominal distention in patients with irritable bowel syndrome or functional bloating. They aimed to determine whether patients' perceived bloating was real, and, if so, whether abdominal-muscle activity was important, as the mechanisms underlying abdominal distension are unknown.

Colonic gaseous filling was performed in 12 patients and 12 healthy controls. Abdominal girth was measured and electromyographic activity was recorded at eight abdominal sites, both before and after the procedure. Patients' perception of bloating was recorded after the procedure. Colonic gaseous filling resulted in significantly greater perceived and actual abdominal distention, compared with controls (P <0.05 for both). Controls showed increased electromyographic activity in all but one abdominal muscle (internal oblique), but patients failed to show any significant increase in the activity of their lower rectus and external oblique muscles; furthermore, their internal oblique muscles showed decreased activity. The decrease in activity correlated with the increase in abdominal girth (r = 0.60, P <0.001).

Although these results indicate that abdominal-muscle activity has a role in abdominal distention, the authors suggest that a combination of pathophysiologic mechanisms is probably responsible for bloating, and that these mechanisms might vary between individuals.