Background and Aims: Duodenal infusion of HCl or lipid delays gastric emptying. The aim of this study was to assess whether this delay was in part caused by mechanical activity of the duodenum. Methods: Synchronized videofluoroscopy and manometry was used in 8 volunteers (5 men and 3 women) to examine contractile and flow patterns during duodenal infusion of 0.9% NaCl, HCl, 5% NaCl, bile, and sodium oleate, each mixed with 20% (wt/vol) barium sulfate. Results: Within 15-30 seconds of infusion, HCl and 5% NaCl induced frequent large-amplitude contractions greater than those induced by 0.9% NaCl. Initially, there was rapid dispersion of HCl followed by prolonged, tonic occlusion of the duodenum. The duodenal diameter decreased compared with that observed during 0.9% NaCl or oleate infusion. In contrast, after infusion of oleate or bile, duodenal diameter increased and there were fewer, smaller-amplitude, nonpropagating contractions with prolonged retention of solutions. Barium (20%; wt/vol) did not influence the motility index of any solution. Conclusions: HCl and 5% NaCl may restrict gastric outflow by inducing tonic occlusion of the duodenum, whereas bile and lipid may delay clearance by decreasing duodenal tone and contractility. Thus, the duodenum may serve as an immediate brake to gastric outflow either by delaying clearance or by offering rapid tonic resistance.
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