Abstract

Background/Aims—While the social significance of flatus derives mainly from its odour, previous studies have focused on the non-odoriferous components of rectal gas. The aims of the present study were to determine the role of sulphur-containing gases in flatus odour and test the efficacy of a device purported to reduce this odour.

Methods—Flatus was quantitatively collected via rectal tube from 16 healthy subjects who ingested pinto beans and lactulose to enhance flatus output. The concentrations of sulphur-containing gases in each passage were correlated with odour intensity assessed by two judges. Odour intensity was also determined after treatment of flatus samples with zinc acetate, which binds sulphydryl compounds (hydrogen sulphide and methanethiol), or activated charcoal. Utilising gas-tight Mylar pantaloons, the ability of a charcoal lined cushion to adsorb sulphur-containing gases instilled at the anus of eight subjects was assessed.

Results—The main sulphur-containing flatus component was hydrogen sulphide (1.06 (0.2) μmol/l), followed by methanethiol (0.21 (0.04) μmol/l) and dimethyl sulphide (0.08 (0.01) μmol/l) (means (SEM)). Malodour significantly correlated with hydrogen sulphide concentration (p⩽0.001). Zinc acetate reduced sulphur gas content but did not totally eliminate odour, while activated charcoal removed virtually all odour. The cushion adsorbed more than 90% of the sulphur gases.

Conclusion—Sulphur-containing gases are the major, but not the only, malodorous components of human flatus. The charcoal lined cushion effectively limits the escape of these sulphur-containing gases into the environment.