Effect of Sigmoid Colon Distension on the Rectosigmoid Junction

Abstract

Purpose The sigmoid colon (SC) is the site of stool storage. The stools accumulate in the SC until, at a certain volume, the mechanoreceptors in the SC wall are stimulated, evoking the sigmoidorectal junction inhibitory reflex with a resulting SC contraction, rectosigmoid junction (RSJ) relaxation and passage of the stools to the rectum. However, the RSJ status during stool accumulation in the SC has been scarcely addressed in the literature. The current study investigated this point. Methods: A balloon-ended tube was introduced into the SC of 21 healthy volunteers [mean age (± SD) 36.8 ± 10.3 years; 15 men and 6 women]. The pressures in the SC and RSJ were measured by means of a perfused tube, at rest and during balloon inflation with carbon dioxide at two rates: slow (3 ml/min) and rapid (150 ml/min). The tests were repeated after individual anesthetization of the SC and RSJ. Results: During slow SC distension up to 80 ml included, the RSJ pressure progressively increased while the SC exhibited no pressure response (p > 0.05). At a distending volume of 100 ml, the pressure in the SC rose (p < 0.01) and declined in the RSJ (p < 0.05), and the balloon was dispelled to the rectum. Rapid SC distension up to 40 ml included, effected no SC pressure response (p > 0.05) while the RSJ showed progressive pressure elevation. At 60 ml distension, the SC recorded a pressure rise (p < 0.001) and the RSJ a pressure decrease (p < 0.05); the balloon was dispelled to the rectum. The pressure in the RSJ did not respond to distension of the anesthetized SC. Conclusion: The study has shown that, during accumulation of stools in the SC, leakage to the rectum seems to be prevented by a reflex action which we call ‘rectosigmoid junction tightening reflex’. This reflex probably acts to control both storage and emptying of the SC contents. Reflex dysfunction might lead to defecation disorders. We suggest that the RSJ tightening reflex be included as an investigative tool in the diagnosis of defecation disorders.