Evaluation of hydrogen excretion after lactulose administration as a screening test for causes of irritable bowel syndrome.

Objective: To determine whether it is possible to separate cases of irritable bowel syndrome associated with excess total hydrogen production (as a surrogate of colonic fermentation; these patients may be offered an exclusion diet as treatment) from other causes of irritable bowel syndrome by determining the amount of hydrogen excreted on patients' breath after oral administration of lactulose.

Design: Comparison of 24-hour hydrogen excretion and breath hydrogen following lactulose in untreated patients fulfilling the Rome criteria for irritable bowel syndrome, normal controls and irritable bowel syndrome patients who had previously failed to improve on an exclusion diet.

Methods: Colonic fermentation was measured by indirect calorimetry over 24 h.