The surgeon must be satisfied with the patient's condition before proceeding with the perineal excision of the rectosigmoid. The estimated blood loss from the abdominal procedure, often more than realized unless accurately determined by the circulating nurse, should be replaced by blood transfusions, and the pulse and blood pressure should be established at a satisfactory level. Some prefer the two-team approach so that the perineal excision is carried out simultaneously with the abdominal procedure.
Historically, Miles then placed the patient on his or her left side in a modified Sims' position. Some surgeons prefer to change the patient to the lithotomy position by adjusting the stirrups to hold the legs. Some place the patient in prone-jackknife to complete the perineal resection. The change in position must be done gently and carefully; sudden shifts have been known to precipitate hypotension and shock. The pulse and blood pressure should be stabilized after the change in position before the final resection is started.
The anus and adjacent skin surfaces are prepared with the usual skin antiseptics. The legs and buttocks are covered with sterile drapes.
The extent of the perineal excision is indicated in Figure 3. If the lesion is low and near the anus, a more radical excision is carried out. Operations for anal cancer will need to be extensive enough to excise the tumor with negative margins. If a large excision is contemplated, preoperative consultation should be made with a plastic surgeon, as myocutaneous flap reconstruction may be necessary. If the dissection has been carried down far enough from above, the perineal excision of the rectum and anus should be accomplished easily without undue loss of blood (Figure 1). To prevent contamination, the anus is sealed securely, either by several interrupted sutures of heavy silk or by a purse-string suture, and the skin is again cleansed with antiseptic solutions (Figure 3). An incision is outlined around the anus with anterior and posterior midline extensions (Figure 2). The skin in the region of the anal orifice is seized with several Allis forceps, and the incision is made through the skin and subcutaneous tissue at least 2 cm away from the closed anal orifice (Figure 4). All blood vessels are clamped and tied to prevent further loss of blood as the operation progresses (Figure 5). The margins of the wound are retracted laterally to assist in the exposure.
The posterior portion of the incision is extended backward over the coccyx, and the anus is tipped upward to enable its attachments to the coccyx to be severed more readily. After the anococcygeal raphe is severed and the presacral space is entered, the accumulated blood from above is suctioned out. The surgeon can then insert the index finger into the presacral space (Figure 6). The finger is swept laterally to identify the levator and muscles on either side. The levator muscle is exposed on one side and, with the finger held beneath it, is divided between paired clamps as far from the rectum as possible (Figure 7). Curved clamps should be applied to the levator ani muscles as they are divided to prevent the retraction of bleeding points. Following the ligation of all bleeding points on one side, a similar division of the levator ani muscles is carried out on the opposite side. Alternatively, the levator muscles may be transected with electrocautery, which can also control bleeding vessels. Vessels that are not easily coagulated with electrocautery should be individually secured with mattress or figure-of-eight absorbable sutures.