The influence of colonic urease activity on 13C-urea breath test

Because of its safety and convenience, the 13 C-urea breath test has recently become a useful tool to detect Helicobacter pylori (Hp) infection. Graham at al observed a rise in 13 C enrichment the 13 C-urea breath test ( 13 C-UBT) for those without Hp infection at 120 minutes after administration of 13 C-urea. They proposed it to be caused by urease activity in the colon. In order to understand the influence of colonic urease activity on 13 C-UBT, we designed a study of colonic 13 C-UBT. We used European standard protocol for 13 C-UBT and 5 permil as the cut-off value. There were 12 patients included in this study (9 men, 3 women, mean age 51.3 years). During the colonoscopic examination, 50 mg, 13 C-urea in 100 ml water was introduced into the cecum through a catheter after the scope had reached that point. Breath samples were collected just before and at 5, 15, 30, 45 & 60 minutes after introduction of labelel urea. The status of Hp infection in the stomach was determined by the usual 13 C-UBT or upper gastrointestinal endoscopic biopsy for a CLO test and histology. Ten of these twelve patients had a positive colonic 13 C-UBT. Half of these ten patients and one of the two with a negative colonic 13 C-UBT were positive for Hp infection in the stomach. We examined the relationship between colonic 13 C-UBT and Hp infectious status in the stomach with Fisher exact test and revealed no statistical significance (p=0.773). We concluded that colonic urease activity caused a positive colonic 13 C-UBT in most tested cases and it seemed unrelated to Hp infection in the stomach.