Effect of colonic distention on ileal motor activity with evidence of coloileal reflex

Chyme delivery from the ileum to the colon is controlled by various neurologic and hormonal factors, many of which remain to be identified. In this report we investigated the effect of colonic distention on ileal motility with the aim of identifying the mechanism of chyme delivery from the ileum to the colon. The right colon of 16 healthy volunteers (12 men and 4 women; mean age 36 ± 9 years standard deviation) was distended by a balloon that was filled with saline solution in increments of 20 ml. The pressure response of the terminal ileum to the colonic distention was recorded by a saline-perfused tube. The test was repeated in nine subjects after the colonic segment around the balloon was anesthetized by xylocaine injection into the colonic wall. Twenty and 40 ml colonic distention produced no significant ileal pressure response. Colonic distention with 60 ml produced an increase in colonic pressure (P < 0.05), as measured by intraballoon pressure, and a decrease in ileal pressure (P < 0.05); a similar response was achieved with 80 ml distention. At 100 ml colonic distention, the balloon was dispelled to the transverse colon. Distention up to 100 ml of the anesthetized colonic segment produced no significant colonic or ileal pressure response. The flow of chyme from the small to the large gut appears to be controlled by a reflex mechanism that we call the ‘coloileal reflex.’ Whenever the right colon is distended with a substantial volume of chyme that increases the intraluminal pressure, it is suggested that ileal relaxation occurs, which delays the emptying of chyme from the ileum.