FUNCTIONAL BOWEL DISEASE Intestinal gas distribution determines abdominal symptoms

Background: Patients with functional gut disorders manifest poor tolerance to intestinal gas loads but the mechanism of this dysfunction is unknown. Aim: Our aims were firstly, to explore the relative importance of the amount of intestinal gas versus its distribution on symptom production, and secondly, to correlate gut motility and perception of gas loads. Subjects: Fourteen healthy subjects with no gastrointestinal symptoms. Methods: In each subject a gas mixture was infused (12 ml/min) either into the jejunum or rectum for one hour during blocked rectal gas outflow, and subsequently gas clearance was measured over one hour of free rectal evacuation. We measured abdominal perception, distension, and gut tone by duodenal and rectal barostats. Results: Similar magnitude of gas retention (720 ml) produced significantly more abdominal symptoms with jejunal compared with rectal infusion (perception score 4.4 (0.4) v 1.5 (0.5), respectively; p,0.01) whereas abdominal distension was similar (15 (2) mm and 14 (1) mm girth increment, respectively). Jejunal gas loads were associated with proximal contraction (by 57 (5)%) and colonic loads with distal relaxation (by 99 (20)%). Conclusion: The volume of gas within the gut determines abdominal distension whereas symptom perception depends on intraluminal gas distribution and possibly also on the gut motor response to gas loads.