Methanogenic flora is associated with altered colonic transit but not stool characteristics in constipation without IBS

Objectives: About 35% of humans have methane-producing gut flora. Methane-producing irritable bowel syndrome (IBS) subjects are generally constipated. In animal models, methane infusion slows intestinal transit. Whether methanogenic flora alters colonic transit or stool characteristics and its relationship to constipation is unclear. The aim of this study was to examine the prevalence and association of methanogenic flora in patients with slow transit (ST) constipation and normal transit (NT) constipation and non-constipated controls.Methods: Ninety-six consecutive subjects with chronic constipation (CC) (Rome III) were evaluated with radio-opaque marker (ROM) transit studies and were classified as ST (>20% ROM retention) or NT. All constipated subjects and 106 non-constipated controls underwent breath tests to assess methane production. Baseline CH₄ of ≥3 p.p.m. was used to define presence of methanogenic flora. Stool frequency and consistency were assessed using a prospective stool diary. Correlation analyses were performed.Results: Forty-eight subjects had ST and 48 had NT. Prevalence of methanogenic flora was higher (<P0.05) in ST (75%) compared to NT (44%) or controls (28%). ST patients had higher methane production compared to NT and controls (>P0.05). NT patients also produced more methane compared to controls (>P0.05). There was moderate(>P0.05) correlation among baseline, peak, and area under the curve (AUC) of methane response with colonic transit but not with stool characteristics.Conclusions: Presence of methanogenic flora is associated with CC. Methane production after carbohydrate challenge and its prevalence were higher in ST than NT, although stool characteristics were similar in both groups. Methane production correlated with colonic transit, suggesting an association with stool transport but not with stool characteristics.