Comparison of scintigraphy and lactulose breath hydrogen test for assessment of orocecal transit - Lactulose accelerates small bowel transit

The lactulose breath test (LET) 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 LET 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 OGTT by LET 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 LET and GECS (without lactulose) are not equivalent measures of OCTT. The standard LET accelerates OGTT and slows gastric emptying. Therefore, lactulose has a direct accelerating effect on small intestinal transit.