INSIGHTS INTO HUMAN COLONIC PHYSIOLOGY OBTAINED FROM THE STUDY OF FLATUS COMPOSITION

To better understand the physiology of colonic gas production, each fl atus passage of 16 subjects over a 4-h period was analyzed by gas chro matography for N-2, O-2, H-2, CO2, CH4, and for odoriferous sulfur-con taining gases. Appreciable intraindividual and enormous interindividua l variability was observed, indicating that each gas passage reflected the interaction of highly variable liberation and/or removal mechanis ms. The predominant flatus gas was CO2, H-2, and N-2 in seven, six, an d three subjects, respectively. Gases produced intraluminally (H-2, CO 2, and CH4) comprised similar to 74% of flatus, and rapid CO2 and H-2 productions were responsible for high passage rates. A positive correl ation between flatus H-2 and CO2 suggested that CO2, like H-2, mainly was a bacterial product. Whereas methanogens and H2S-producing bacteri a usually are mutually exclusive in feces, CH4 and H2S did not negativ ely correlate, indicating coexistence of both organisms in the colon. We conclude that analysis of flatus composition provides a novel means of assessing colonic physiology, particularly ongoing bacterial metab olism throughout the unperturbed colon.