The hypertonic rectosigmoid junction: description of a new clinicopathologic entity causing constipation.

A physiological sphincter exists at the rectosigmoid junction; this rectosigmoid sphincter (RSS) relaxes on sigmoid colon contraction and contracts on rectal contraction. Eight cases of RSS hypertonia are presented herein. Six women and two men (mean age, 44.2 +/- 10.3 years) complained of chronic constipation of 9.6 +/- 6.2 years' duration. They had had normal bowel habits before that time. Anorectal physiologic studies were performed. Intestinal transit was delayed by the accumulation of pellets in the sigmoid colon. Defecography and electromyography of the external anal sphincter and levator ani muscle were normal. The resting pressure was normal in the sigmoid colon, rectum, and rectal neck (p > 0.05) but elevated in the RSS (p < 0.01). The sigmoidorectal inhibitory and excitatory reflexes were absent. Biopsies from the sigmoid colon and rectum showed normal histologic findings, but those from the RSS were aganglionic. A diagnosis of RSS "achalasia" was made. Five of the eight patients had improvement as a result of RSS dilatation. The remaining three patients underwent sigmoidomyotomy. The eight patients are now 9 to 38 months without recurrence of constipation. Rectosigmoid junction achalasia constitutes a clinicopathologic entity that should be considered in the etiology of constipation.