Role of the rectum in the physiological and clinical results of coloanal and colorectal anastomosis after anterior resection for rectal carcinoma.

This study investigated the relationships between length of residual anorectum, anorectal physiological function and clinical outcome after anterior resection for rectal carcinoma. Thirty-four patients were studied a median of 13 (range 4-100) months after anterior resection. They were compared with a control group of ten patients who had undergone sigmoid colectomy for carcinoma without rectal excision. Resting anal pressure was found to be lower after coloanal than after colorectal anastomosis, and the capacity of the (neo)rectum was less after coloanal than after colorectal anastomosis. The (neo)rectoanal inhibitory reflex was found to be present in each patient, but maximum anal pressure during this 'sampling' reflex was significantly lower (P < 0.01) after coloanal than after colorectal anastomosis, and the volume required for maximal inhibition of the sphincter was also less (P < 0.01). At 1 year after operation, median bowel frequency was greater after coloanal (4 per day) than after colorectal (2 per day) anastomosis and the degree of urgency of defaecation was also greater (P < 0.01). Quality of life in terms of anorectal function after anterior resection is thus significantly influenced by the length of rectum that is left. This, in turn, influences the functional capacity of the neorectum and the degree of inhibition of the anal sphincter during the neorectoanal inhibitory reflex.