DECREASE IN THE ANORECTAL PRESSURE-GRADIENT AFTER LOW ANTERIOR RESECTION OF THE RECTUM - A STUDY USING CONTINUOUS AMBULATORY MANOMETRY

PURPOSE: Changes in anorectal function alter low anterior resection of the rectum (LAR) often lead to symptoms of urgency and frequency of d efecation, the anterior resection syndrome. It has been reported that preservation of part of the rectum improves clinical results, but why this should be remains unclear.,METHODS: We have carried out continuou s ambulatory manometric studies in two groups of patients: 11 patients , a median of 11 (range, 5-96) months after LAR, in whom the median an astomotic level above the anal high-pressure zone was 0 (range, 0-2) c m; 9 patients, a median of 6 (range, 3-12) months after sigmoid colect omy, in whom the rectum remained in situ and who acted as controls. RE SULTS: Comparing the LAR group with controls, resting anal pressures w ere lower, median 68 (range 27-102) cm H2O vs. 95 (45-116) cm H2O (P < 0.05), and neorectal pressures were higher, 25 (0-48) cm H2O vs. 10 ( 0-10) cm H2O (P < 0.01). Thus the anorectal pressure gradients were le ss, 34 (0-74) cm H2O vs. 81 (35-113) cm H2O (P < 0.01). Slow-wave acti vity in the anal sphincter was present in six patients (55 percent) af ter coloanal anastomosis and eight patients (89 percent) after sigmoid colectomy. Sampling episodes were seen in only two patients (18 perce nt) after coloanal anastomosis and five patients (56 percent) after si gmoid colectomy. When clinical endpoints were compared (LAR vs. contro ls), bowel frequency in 24 hours was higher, 5 (3-8) vs. 2 (1-3) (P < 0.01); fecal leakage was more common, affecting seven patients (64 per cent) vs. one patient (11 percent) (P < 0.05), and urgency of defecati on was also more common. CONCLUSIONS: The inferior clinical results ob served after LAR compared with the results after sigmoid colectomy are thus in part because of higher neorectal pressure acting on a weakene d sphincter mechanism. These observations lend support to the idea tha t neorectal capacity should be increased in patients who undergo low a nterior resection.