A study of intracolonic hydrogen and methane levels during colonoscopy.

Gas samples were obtained during colonoscopy for analysis. Patients were prepared with polyethylene glycol (PEG) (N = 23), phosphate enema (N = 34) and mannitol (N = 4). Air insufflation was used in all procedures. High concentrations of hydrogen were detected in 3 out of 38 gas samples in the PEG group, in 2 of 41 samples in the phosphate enema group and in one of the 8 samples in the mannitol group. All patients had a coexisting intracolonic oxygen concentration > 5%. The results suggest that potentially explosive concentrations of hydrogen may occur after conventional bowel preparations, and that insufflation of carbon dioxide during polypectomy should be a routine.