Study of the effect of colonic mass movements on the rectosigmoid junction with evidence of colo-rectosigmoid junction reflex.

Mass movements of the left-sided colon bring the colonic material contained in it to the sigmoid colon. The cause why the colonic contents do not pass directly to the rectum but stop short of the rectosigmoid junction (RSJ) was studied. The study comprised 10 healthy volunteers (mean age 39.2 +/- 10.2 years; 8 men, 2 women). A condomended tube was introduced into the descending colon (DC) per anum. The pressure response of the DC, sigmoid colon (SC), and RSJ to condom inflation with carbon dioxide (CO2) in increments of 10 ml was recorded by means of a three-channel microtip catheter. The responses were registered upon inflation of the upper, middle, and lower third of the DC. The test was repeated after individual anesthetization of the descending colon and the RSJ on separate days. Colonic distension with 10 and 20 ml CO2 produced no significant pressure changes in the DC, SC, and RSJ (p > .05); 30 ml distension effected a pressure rise in both the DC (p < .01) and RSJ (p < .05), but no change in the SC pressure (p > .05); and 40, 50, and 60 ml distension produced pressure changes similar to those obtained with 30 ml distension. The RSJ pressure responded to distension of the saline-injected but not of the anesthetized DC. Thus, the RSJ response to colonic distension affirms the hypothesis of the possible involvement of a reflex, which we term colo-RSJ reflex. This reflex seems to regulate the passage of stools from the colon to the rectum. Further studies are required to investigate its role in the diagnosis of defecation disorders.