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 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 plus computed tomography (CT) imaging.
In males, an indwelling catheter is inserted into the bladder the morning of operation 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 0 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.
A midline incision is made and extended to the left and above the umbilicus. A self-retaining retractor is inserted.
With the left hand, the surgeon thoroughly explores the abdomen from above downward, palpating first the liver to ascertain the presence or absence of metastases and then the region of the aorta and common iliac and hemorrhoidal vessels for evidence of lymph gland involvement. Finally, by palpation and inspection, the surgeon determines the extent and resectability of the growth itself (Figure 1). The inferior mesenteric artery and vein may be ligated distal to the origin of the left colic artery or at its point of origin from the aorta before the tumor is mobilized, but after identification of the ureters.
After the small intestine has been walled off in a plastic bag, the next procedure is the mobilization of the sigmoid, which is usually anchored in the left iliac fossa. The sigmoid is grasped and reflected medially in order that the surgeon may obtain a clear view of the fibrous bands that anchor the sigmoid to the reflection of the peritoneum of the left pelvic wall (Figure 2). The adjacent adhesive bands are divided with long curved scissors or electrocautery, and the peritoneal reflection is retracted laterally with forceps. Following this procedure, the sigmoid is usually mobilized easily toward the midline. The peritoneal surface on the left side of the colon is picked up with forceps and divided with long, curved, blunt-nosed Metzenbaum scissors, which are gently introduced downward beneath the peritoneum to separate the underlying structures, such as the left spermatic, or ovarian, vessels or ureter, from the peritoneum to avoid their accidental injury. The peritoneum is incised down to the cul-de-sac on the left side (Figure 3).
The next important step in the operation is the visualization of the left ureter throughout its course over the pelvic brim and down to the bladder. This is very important because, on the left side, the ureter may be in close proximity to the root of the mesentery of the rectosigmoid and may be included in the division of the latter structures unless it is carefully retracted to the left side of the pelvis (Figure 4). The ureter will respond with peristaltic waves that progress along its length after it is pinched with forceps.
The next step involves the division of the peritoneum on the right side of the rectosigmoid. The same technique that has been described for the left side may be utilized, or the surgeon may mobilize the rectosigmoid over the pelvic brim from the left side by blunt finger dissection. The fingers of the surgeon's left hand can be passed completely behind the bowel toward the right side. With the fingers used as blunt dissectors, the right peritoneal reflection can be tented upward, separating it from the underlying structures, including the right ureter. This enables the surgeon to divide the peritoneum readily and safely with scissors or electrocautery (Figure 5).