Lactose-[13C]ureide breath test:: A new, noninvasive technique to determine orocecal transit time in children

Background: The lactose-[C-13]ureide breath test (LUBT) is a novel, noninvasive test to determine orocecal transit time. Lactose ureide resists the action of brush border enzymes and is metabolized by colonic bacteria. The purpose of the present study was to adapt this breath test for children of various age groups and to determine whether it can be applied in infants, newborns, and preterms to study the development of small intestinal motility. Methods: In a group of 20 children (3-17 years) in vitro stool analysis and in vivo LUBT results were compared. From each subject a blank stool sample and a sample produced after induction with unlabeled lactose ureide were incubated with 10 mg lactose-[C-13]ureide in small, closed bottles. Ten-milliliter CO2 samples were aspirated from the bottles using a needle and a syringe every 30 minutes for 24 hours. All children performed the breath test after induction of 500 mg unlabeled lactose ureide three times the prior day. A liquid test meal (chocolate milk) with 250 mg lactose-[C-13]ureide was ingested. Breath samples were collected every 15 minutes for 10 hours. In a second group of 32 children (age range, 0-3 years) consisting of 6 children between 1 and 3 years of age, 6 infants between 6 and 12 months, 13 infants between 0 and 6 months, and 7 preterm infants, only the in vitro stool analysis was performed. Stools were collected for stool incubation, as described. Results: The mean orocecal transit time in the group of 20 children aged 3 to 17 years was 255 minutes (range, 165-390 minutes). Stool incubations demonstrated a clear (CO2)-C-13 peak in all infants aged more than 8 months, indicating that their colonic bacterial enzymic activity hydrolyses lactose ureide. However, in all infants aged less than 6 months and in preterm infants, the (CO2)-C-13 signal was absent, indicating that those subjects were unable to hydrolyze lactose ureide. Conclusion: Infants aged less than 6 months do not host the appropriate bacterial enzymic activity for splitting lactose ureide. The authors conclude that the LUBT can be applied in infants aged more than 8 months, after weaning to solid foods, to determine orocecal transit time.