Influence of oral mannitol bowel preparation on colonic microflora and the risk of explosion during endoscopic diathermy.

Oral mannitol has been widely accepted as the bowel preparation of choice for colonoscopy and elective colorectal operation because it is well tolerated by patients. Recent concern has been expressed regarding the risk of explosion and sepsis using oral mannitol because it may provide a nutrient for certain gas-producing bacteria in the colon. Samples of colonic contents aspirated at operation were compared in patients prepared by oral mannitol, by whole bowel irrigation, mannitol preceded by 48 h of oral antibiotics (neomycin with metronidazole) and in patients who did not undergo any preparation. Significantly higher counts of gas-producing Escherichia coli were recovered from patients prepared with mannitol alone compared with whole bowel irrigation or mannitol preceded by oral antimicrobials. These data are consistent with the hypothesis that fermentation of mannitol by Escherichia coli is responsible for the production of potentially explosive gas mixtures after oral mannitol preparation and may also explain the increased incidence of sepsis when oral mannitol is used for bowel preparation.