Fluid loading of the human colon: Effects on segmental transit and stool composition

Abstract

Background: Because segmental storage by the colon is relevant to diarrheal states, we quantified colonic transit in 13 healthy volunteers. Methods: We infused radiolabelled liquids and solids into the cecum. Gamma camera images were obtained for 48 hours and counts measured in ascending (AC), transverse (TC), descending (DC), and rectosigmoid (RS) colons. Bowel movements were scored for consistency and stool outputs of isotopes were quantified. Results: No volunteers developed diarrhea. Times for isotopes to traverse AC and TC were shorter with rapid infusions (P < 0.001). Counts remaining in AC and TC were also correlated with infusion volumes for 9 hours but not thereafter. Solids were initially delayed in AC but solids and liquids were stored equally in TC. Transit through DC was rapid, but RS stored contents for many hours. First appearance of counts in stools and total counts excreted after 48 hours were not dependent on the infusion rate. Fecal consistency and water content correlated significantly with colonic transit times. Conclusions: Fluids moved ahead of solids in the AC, but liquids and solids were stored equally in the TC. The DC acted mainly as a conduit during fluid overload but the RS stored both isotopes extensively. Stool consistency was a valid reflection of total colonic transit.