Does Colonic Transit Time Affect Colonic pH?

Abstract

AIM: To assess the effect of colonic transit time (CTT) on pH in the proximal and distal colon. METHODS: CTT and pH in different regions of the colon were assessed using a wireless capsule manometry system. Healthy controls and patients with chronic constipation based on Rome II criteria were studied. Mean pH was determined in time quartiles of colonic transit, in the first 15 minutes after entry of the capsule into the cecum, and in the last 15 minutes prior to capsule exit from the body and correlated with CTT. RESULTS: There was a weak, but significant correlation between CTT and pH in the distal colon (R=0.20, p=0.01 in the 15 minutes prior to body exit, and R=0.22, p=0.01 in the fourth quartile of CTT). No correlations between CTT and pH were found in the proximal colon. Patients with slow transit constipation tended to have a greater rise in pH from the proximal to the distal colon than those with normal transit constipation or healthy controls. CONCLUSION: Longer CTT is associated with an increase in pH in the distal, but not proximal colon. The higher pH in the distal colon in slow transit constipation may affect important physiological and pathological processes.