This article investigates the location and magnitude of altered intestinal bacterial fermentation in IBS and its clinical subtypes.

Abstract

OBJECTIVES

Dysbiosis leading to abnormal intestinal fermentation has been suggested as a possible etiological mechanism in irritable bowel syndrome (IBS). We aimed to investigate the location and magnitude of altered intestinal bacterial fermentation in IBS and its clinical subtypes.

METHODS

One hundred fourteen IBS patients who satisfied Rome III criteria and 33 healthy controls (HC) were investigated. Intestinal fermentation was assessed using two surrogate measures: intestinal intraluminal pH and fecal short chain fatty acids (SCFAs). Intraluminal pH and intestinal transit time were measured in the small and large bowel using a wireless motility capsule (SmartPill™) in 47 IBS and 10 HC. Fecal SCFAs including acetate, propionate, butyrate and lactate were analyzed by capillary gas chromatography in all enrolled subjects. Correlations between intestinal pH, fecal SCFAs, intestinal transit time and IBS symptom scores were analyzed.

RESULTS

Colonic intraluminal pH levels were significantly lower in IBS patients compared to HC (total colonic pH, 6.8 for IBS vs. 7.3 for HC, P = 0.042). There were no differences in total and segmental pH levels in the small bowel between IBS patients and HC (6.8 vs. 6.8, P = NS). The intraluminal colonic pH differences were consistent in all IBS subtypes. Total SCFAs level was significantly lower in C-IBS patients than in D-IBS and M-IBS patients and HC. The total SCFAs level in all IBS subjects was similar with that of HC. Colonic pH levels correlated positively with colon transit time (CTT) and IBS symptoms severity. Total fecal SCFAs levels correlated negatively with CTT, and positively with stool frequency.

CONCLUSIONS

Colonic intraluminal pH is decreased, suggesting higher colonic fermentation, in IBS patients compared with HC. Fecal SCFAs are not a sensitive marker to estimate intraluminal bacterial fermentation.