Effect of sigmoid colon distension on the rectosigmoid junction - Description of the rectosigmoid junction tightening reflex and its clinical implications

Purpose The sigmoid colon (SC) is the site of stool storage. The stools acc umulate in the SC until, at a certain volume, the mechanoreceptors in the S C wall are stimulated, evoking the sigmoidorectal junction inhibitory refle x with a resulting SC contraction, rectosigmoid junction (RSJ) relaxation a nd passage of the stools to the rectum. However, the RSJ status during stoo l accumulation in the SC has been scarcely addressed in the literature. The current study investigated this point. Methods: A balloon-ended tube was i ntroduced 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 measu red 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 te sts were repeated after individual anesthetization of the SC and RSJ. Resul ts: During slow SC distension up to 80 mt included, the RSJ pressure progre ssively increased while the SC exhibited no pressure response (p > 0.05). A t a distending volume of 100 mi, the pressure in the SC rose (p < 0.01) and declined in the RSJ (p < 0.05), and the balloon was dispelled to the rectu m. Rapid SC distension up to 40 mt included, effected no SC pressure respon se (p > 0.05) while the RSJ showed progressive pressure elevation. At 60 mi distension, the SC recorded a pressure rise (p < 0.001) and the RSJ a pres sure decrease (p < 0.05); the balloon was dispelled to the rectum. The pres sure in the RSJ did not respond to distension of the anesthetized SC. Concl usion: The study has shown that, during accumulation of stools in the SC, l eakage to the rectum seems to be prevented by a reflex action which we call 'rectosigmoid junction tightening reflex'. This reflex probably acts to co ntrol both storage and emptying of the SC contents. Reflex dysfunction migh t lead to defecation disorders. We suggest that the RSJ tightening reflex b e included as an investigative tool in the diagnosis of defecation disorder s. Copyright (C) 2000 S. Karger AG,Basel.