Abdominoperineal resection of the lower bowel is the operation of choice for very low rectal malignancies that involve the sphincter complex or cannot be removed with a 2-cm distal margin. In special circumstances, young patients may be candidates for a coloanal anastomosis, whereas others may be candidates for local wide excision and adjuvant treatment for low-grade superficial lesions. The surgeon must be familiar with all methods, including resection of the tumor and anastomosis of the intestine within the hollow of the sacrum.
The patient’s general condition must be studied and improved as much as possible, since the operation is one of the considerable magnitude. Unless there is evidence of acute or subacute obstruction, the patient is placed on a liquid diet for a day. Most patients receive a bowel preparation the afternoon or evening prior to surgery. Following complete evacuation of the colon with laxatives or purgative, appropriate nonabsorbable antibiotics may be given. Parenteral antibiotic coverage is given just prior to surgery. In the presence of low-lying tumors, it may be advisable to evaluate by cystoscopy whether or not the bladder or other portions of the genitourinary tract are involved. Basal carcinoembryonic antigen levels are determined before and after resection of the neoplasm. The extent of extramural spread or fixation to adjacent organs may be evaluated with endorectal ultrasound or MRI plus computed tomography (CT) imaging.
In males, an indwelling catheter is inserted into the bladder at the beginning of the procedure to maintain complete urinary drainage throughout the procedure and to aid in identifying the membranous urethra. Indwelling catheter drainage of the bladder in females is likewise advisable.
Currently, rectal carcinomas below the level of the peritoneal reflection in the pouch of Douglas are usually given combined radiation therapy and chemotherapy prior to surgery.
General anesthesia with endotracheal intubation and muscle relaxants is the preferred method.
The surgeon stands on the patient’s left side. Most prefer a two-team approach with the patient in the semilithotomy position using Allen stirrups. This allows the perineal portion of the procedure to be carried out either simultaneously or after the abdominal portion without redraping, etc. A folded sheet is placed under the lower back so that the buttocks are lifted up off the bed, allowing better access to the posterior part of the perineal dissection. After an enema with a povidone–iodine solution, the anus is sutured shut at the anal verge (not distal to it) with a running-locked o silk suture. A moderate Trendelenburg position may facilitate retraction, as long as it is well tolerated by the patient.
The lower abdomen, perineal, and rectal areas are prepared in the usual manner.