Reassessment of the role of methane production between irritable bowel syndrome and functional constipation.

Background & Aims: Modifications of intestinal gas due to changes in microbiota may produce different symptoms. Our aim was to assess whether different patterns of hydrogen (H-2) and methane (CH4) excretion were related to some intestinal disturbances. Methods. Six hundred and twenty-nine consecutive patients underwent a 50g-glucose breath test (GBT) on account of intestinal symptoms, which were evaluated by means of a questionnaire. "H-2-producers" and "CH4-producers" were defined as with the presence of H-2 peak >12ppm more than the basal sample and mean CH4 excretion of 2ppm, respectively. Forty healthy subjects were studied as controls. Results. A small intestinal bacterial overgrowth was found in 45 cases (7.2%) and was associated with older age (p=0.0122). Methane production occurred in 32.3% of the study population. Methane excretion was strictly related to chronic constipation (p<0.001). Median CH4 excretion was higher in constipated patients compared with patients with normal daily stools (p=0.0406) and even more with patients complaining of diarrhea (p=0.0011). Different criteria for defining "methane-producers" provided similar results. Mean methane excretion of "methane producers" was 30.3ppm in functional constipation and 21.5ppm in constipation-irritable bowel syndrome (C-IBS) (p=0.0458). Conclusions. Methane excretion is clearly associated with alterations in intestinal motility, particularly favouring those with constipation. Mean methane excretion was higher in subjects suffering from functional constipation than C-IBS. Mean methane excretion >= 2ppm appears to be an appropriate term to define "methane-producers"