A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. Reversion to normal defecation after combined excision operation and end colostomy for rectal cancer.

Twenty-one patients with combined excision operation for rectal cancer were subjected to electromyographic study of the levator ani muscle, the puborectalis muscle, and the external anal sphincter. Myoelectric activity of the puborectalis and levator ani muscles was detected in 12 patients, 6 of whom had normal activity of both muscles. Of the remaining six patients, there was reduced activity of the levator ani muscle in four and of the puborectalis muscle in all six. These patients underwent training and electric stimulation of these muscles. To verify the myoelectric findings, 15 specimens removed at combined excision operation were examined grossly and microscopically for the muscles removed at operation. Eight specimens were found to be free of the levator and puborectalis muscles, which indicated that these muscles were not excised. The 12 patients with myoelectrically active levator and puborectalis muscles were operated on to restore defecation by way of the normal perineal route. The technique comprises freeing of the colostomy and mobilization of the entire left side of the colon. The perineal scar is then excised and the colonic end fixed to the perineal skin and thus is controlled by the levator and puborectalis muscles. Full fecal control was achieved in seven patients and incomplete control in five. It is concluded that excision of the levator ani muscle, the puborectalis muscle, and the external anal sphincter should not be considered a standard part of the radical operation for cancer of the lower or middle third of the rectum, and that a combined excision operation has no place in the treatment of rectal cancer.