The lactulose breath test (LBT) and gastroenterocolonic scintigraphy (GECS) can both be used to measure orocecal transit time (OCTT). The aims of this study were (1) to measure OCTT by LBT and GECS and (2) to determine whether lactulose alters orocecal transit.
Methods: Eight normal subjects underwent simultaneous breath hydrogen testing, GECS, and duodenal manometry while receiving either 10 g lactulose or placebo with a radiolabeled solid/liquid test meal during two studies. There was a good correlation between OCTT by LBT and GECS when performed simultaneously (r = 0.95; P < 0.001). OCTT by GECS with lactulose was significantly faster (P = 0.004) than by GECS without lactulose, despite no change in gastric emptying of liquids and slowing of gastric emptying of solids (P = 0.02). The postprandial duodenal motility index was greater with lactulose than with placebo (P = 0.031). This study demonstrates that LBT and GECS (without lactulose) are not equivalent measures of OCTT. The standard LBT accelerates OCTT and slows gastric emptying. Therefore, lactulose has a direct accelerating effect on small intestinal transit.