Is rectosigmoid response to food modulated by proximal colon stimulation?

Rectosigmoid motor activity and postprandial breath hydrogen levels were monitored in eight healthy males under basal conditions and for 3 1/2 hr after a meal (beefburger and breadroll and ice cream incorporating 20 g lactulose). Within minutes of ingestion there was a significant increase in motility index (P less than 0.05) and also an initial temporary rise in breath hydrogen. A late increase in motor activity occurred in seven of eight subjects 123 +/- 19 min after the meal and was temporally related to the beginning of a second, much larger rise in breath hydrogen (r = 0.99; P less than 0.01). The close association between the timing of the rises in breath hydrogen and rectosigmoid motor activity would support the possibility that the latter may be generated by chemical or mechanical stimulation of the proximal colon.