Mechanisms of intestinal gas retention in humans: impaired propulsion versus obstructed evacuation

To explore the clinical role of intestinal gas dynamics, we investigated tw o potential mechanisms of gas retention, defective propulsion and obstructe d evacuation. In healthy subjects, a gas mixture was continuously infused i nto the jejunum (4 ml/min) 1) during a 2-h control period of spontaneous ga s evacuation and 2) during a 2-h test period either with impaired gut propu lsion caused by intravenous glucagon (n = 6) or with obstructed (self-restr ained) anal evacuation (n = 10) while anal gas evacuation, symptom percepti on (0-6 scale), and abdominal girth were measured. Impaired gut propulsion and obstructed evacuation produced similar gas retention (558 +/- 68 ml and 407 +/- 85 ml, respectively, vs. 96 +/- 58 ml control; P < 0.05 for both) and abdominal distension (8 <plus/minus> 3 mm and 6 +/- 3 mm, respectively, vs. 1 +/- 1 mm control; P, 0.05 for both). However, obstructed evacuation increased symptom perception (2.3 +/- 0.6 score change; P < 0.05), whereas gas retention in the glucagon-induced hypotonic gut was virtually unperceiv ed (-0.4 <plus/minus> 0.7 score change; not significant). In conclusion, th e perception of intestinal gas accumulation depends on the mechanism of ret ention.