Introduction Fermentation of undigested carbohydrates by the colonic microbiota is an important part of maintaining a healthy colonic environment. However, excessive fermentation is thought to play a role in exacerbating symptoms of bloating, distension, pain and alternating bowel habit. By-products of the fermentation process include short chain fatty acids (SCFA’s) which reduce caecal pH. Measurement of caecal pH therefore provides an opportunity to objectively quantify aspects of fermentation but has been technically challenging to achieve. In this retrospective study, we compared intestinal pH and pressure profiles using an ingestible wireless motility capsule (WMC) (SmartPill, Buffalo, US) in healthy controls and patients with symptoms of bloating, distension, pain and alternating bowel habit.

Methods Motility and pH data were reviewed from 16 healthy controls (Cx) and 16 age and sex matched patients (Px) that had undergone the WMC study using a standardised protocol. Motility measures (area under curve (AUC)) were anchored around known anatomical landmarks as identified by compartmental pH changes. 60-minute epochs were used to quantify antral, duodenal, ileal, caecal and distal colonic contractility. The maximum and minimum pH was measured either side of the ileo-caecal junction. All data are presented as means (±95% CI).

Results No differences were seen in any of the motility parameters, compartmental transit times or maximal ileal pH between the two groups. Minimum caecal pH was significantly lower in patients compared to control (Px = 5.14 ± 0.14 v Cx = 6.12 ± 0.16, p < 0.0001). The 95% CI for maximum pH drop across the ICJ in health was 1.65 units. There was a significant correlation between caecal pH and caecal contractility (r = 0.498, p = 0.05).

Conclusion In this study, we have shown that patients with lower abdominal symptoms typically associated with, but not limited to, conditions such as irritable bowel syndrome (IBS) have a significantly lower caecal pH compared to controls. This low pH environment is maintained by fermentation and subsequent SCFA production. SCFA have been shown to inhibit colonic motility in-vitro and contractility as measured by the WMC was correlated with caecal pH. With the recent success of anti-biotic therapy and low fermentable diets in the treatment of lower bowel symptoms in IBS, measurement of caecal pH using the WMC provides an objective and quantifiable biomarker of fermentation. This may be used to sub-classify patients with a broad spectrum of GI disorders and identify those that may benefit most from antibiotic, probiotic and dietary interventions providing novel insights into the pathophysiological mechanisms of lower GI symptoms.

Disclosure of Interest A. Hobson Paid Instructor for: Given Imaging, S. Mohammed: None Declared, G. Dukes Employee of: GSK, M. Scott: None Declared