Denervation of the neorectum as a potential cause of defecatory disorder following low anterior resection for rectal cancer

PURPOSE: The aim of this study was to determine whether denervation of the sigmoid colon during low anterior resection contributes to the postoperative motility characteristics of the neorectum and to the defecatory function of patients. METHODS: Sixty-seven patients who underwent either low or ultralow anterior resection for rectal cancer were evaluated. In accordance with the length of denervated neorectum, each patient was assigned to either the shortdenervation or long-denervation group, determined by whether the inferior mesenteric artery was divided. Colonic propagated contraction was then measured by means of intraluminal pressure monitoring. Transit time was calculated with orally administered radiopaque markers. RESULTS: Propagated contraction down to the neorecturn was significantly less common in the long-denervation group (14/36) than in the short group (12/15, P < 0.05), whereas spastic minor contraction at the neorectum was significantly more common in the long-denervation group (21/36) than the in short group (3/15, P < 0.05). Colonic transit time below the sigmoid colon was significantly longer in long group (6.4 hours) than in the short group (3.4 hours, P < 0.01). Although motility disorder of the neorectum was correlated with clinical defecatory malfunctions, including multiple evacuations, urgency, and soiling, no significant correlation was noted between the length of the denervated neorecturn and the defecatory disorders. CONCLUSIONS: Motility of the neorectunt following low anterior resection appears degraded by intraoperative maneuvers that cause denervation of the remnant sigmoid colon. Motility disorder of the neorectum, but not the length of the denervated neorecturn causing the disorder, correlates well with several defecatory malfunctions. This finding suggests that postoperative defecatory disorder as a result of low anterior resection is caused by many factors in addition to denervation of the neorectum.