Glucose malabsorption associated with rapid intestinal transit.

Twenty-five patients with chronic diarrhea were studied with a combined glucose-hydrogen breath test (GHBT) and nuclear transit scan to elucidate the role of abnormal transit in the pathogenesis of diarrhea. Eight of the 25 patients demonstrated both a rapid orocecal transit time by nuclear scan (less than 30 min) and a positive hydrogen breath test (greater than 20 ppm increase in H2 after a 50-g glucose challenge). Because these individuals had no anatomic abnormalities predisposing to small bowel bacterial overgrowth, it is probable that they demonstrated colonic bacterial metabolism of carbohydrate secondary to glucose malabsorption associated with rapid small bowel transit. The eight patients exhibited some form of autonomic dysfunction generally related to systemic disease. Thus, there may be a subset of patients with chronic diarrhea related to rapid intestinal transit. A combined GHBT-nuclear transit scan permits accurate identification of such individuals and improves the accuracy of hydrogen breath tests in the diagnosis of bacterial overgrowth.