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Concept of the Primary Continent Mechanism

Ahmed Shafik, MD, PhD; Ali A. Shafik, MCh, MD; Olfat El Sibai, MD, PhD; Ismail Ahmed, MCh, MD; Randa M. Mostafa, MD, PhD

Arch Surg. 2006;141:23-26.

Hypothesis  At mass contraction of the descending colon, the colonic contents stop at the sigmoid colon (SC) and do not pass directly to the rectum. We investigated the hypothesis that a continent mechanism seems to exist at the rectosigmoidal junction (RSJ), preventing the direct passage of stools from the descending colon to the rectum.

Methods  The SC in 16 healthy volunteers (mean ± SD age, 38.6 ± 10.2 years; 9 men and 7 women) was distended with an isotonic sodium chloride solution–filled balloon, and the pressure response of the RSJ and the rectum was recorded at rapid and gradual filling of the balloon. The test was repeated after the SC and RSJ were anesthetized separately.

Results  Rapid SC balloon distension with a mean ± SD of 52.1 ± 3.6 mL of isotonic sodium chloride solution effected an RSJ pressure increase to a mean ± SD of 67.8 ± 18.4 cm H₂O (P<.01) with no rectal pressure response (P>.05). Slow SC filling produced a progressive increase in RSJ pressure but no rectal pressure change. At a mean ± SD SC distending volume of 86.3 ± 4.1 mL, the RSJ pressure decreased to 9.6 ± 2.8 (P<.01), and the balloon was dispelled to the rectum; rectal pressure increased (P<.001), and the balloon was expelled to the exterior. The RSJ pressure did not respond to distension of the anesthetized SC.

Conclusions  Contraction of the RSJ at rapid SC distension with big volumes implies a reflex relationship that we call the RSJ guarding reflex. This reflex seems to prevent the descending colon contents from passing directly to the rectum. It is considered the first continent reflex and may serve as an investigative tool in the study of fecal incontinence.

Author Affiliations: Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo (Drs Ahmed Shafik, Ali A. Shafik, and Ahmed), Department of Surgery, Faculty of Medicine, Menoufia University, Shebin El-Kom (Dr El Sibai), and Department of Physiology, Faculty of Medicine, Sharkia University, Banha-Zagazig (Dr Mostafa), Egypt.