Position the patient supine on the operating table. Use either specially constructed leg supports or homemade outrigger “skis” to support the legs in moderate abduction with mild flexion at the hips and knees (Fig. 101.2A). The buttocks should extend slightly over the end of the operating table. Comfortable access to the perineal region should be available for the operating surgeon. Avoid the use of standard lithotomy stirrups, because these produce excessive flexion at the hip and knee and have been associated with vascular complications when used for lengthy procedures. Close the anus securely with a purse-string suture. Prepare and drape the anterior abdomen and perineal region. Place a towel over the perineum to provide temporary coverage until access is required. The initial phase of the dissection is done through the abdomen, with the second assistant standing between the legs of the patient. The instrument nurse should stand on a stool. Do not proceed with the perineal dissection unless you are certain that sphincter preservation will not be possible.

A lower midline incision provides good exposure to the lower abdomen and pelvis. Make the incision from just above the umbilicus to the level of the pubis. Explore the abdomen. Mobilize the left colon as described in Chapter 81. Carry the peritoneal incisions anteriorly, about 1 cm up on the bladder, meeting in the midline between the bladder and the rectum.

Identify both ureters and surround them with Silastic loops. After the peritoneal incision has been completed and both ureters have been identified, divide the sigmoid colon at the point selected. Pass a hand behind the inferior mesenteric artery in the avascular plane just anterior to the vertebral bodies. Locate both ureters and confirm that they have not been included with the mesentery of the colon. Serially divide the mesentery of the colon with clamps. Using laparotomy pads, pack the proximal left colon up in the left upper quadrant.

The distal sigmoid is now completely free and can be circumferentially elevated from the pelvis, allowing access to the rectum. First, complete the posterior dissection. Elevate the sigmoid colon and initiate sharp dissection with Metzenbaum scissors in a plane just superficial to the sacrum (Fig. 101.2B). At the beginning of this dissection, you will see the aorta and common iliac vessels should be seen through a very light veil of areolar tissue. A few bands passing directly posterior between the colon and the presacral space can be divided using electrocautery or scissors. A middle sacral artery is usually present and should be secured with hemoclips. The colon should elevate easily, and a very thin glistening layer of retroperitoneal areolar tissue should be left intact over the presacral venous plexus. You should be able to dissect this plane easily by hand. If difficulty is encountered, it is possible that you are in the wrong plane; stop and reassess the situation. Torrential bleeding from the presacral venous plexus may follow inadvertent entry into this plexus. Conversely, remaining in the correct plane of dissection not only minimizes bleeding but also helps preserve autonomic nerves in the region. Dissection in the hollow of the sacrum should proceed readily until the tip of the coccyx is palpable and the rectosigmoid is elevated up on the hand. Check the hollow of the sacrum for hemostasis.

Next, turn your attention to the anterior dissection. Connect the peritoneal incisions laterally across the posterior surface of the bladder (Fig. 101.2C). Place three long hemostats, such as Crile hemostats, on the peritoneal reflection overlying the bladder. By sharp and blunt dissection, free the rectum from the posterior wall of the bladder until the seminal vesicles (in the male) are encountered (Fig. 101.2D). Carry this dissection down below the seminal vesicles, taking Denonvilliers fascia with the specimen. As noted in Figure 101.6, the posterior wall of the vagina is commonly excised with the specimen in a female. In this case, the anterior dissection need only proceed to a convenient point below the uterine cervix.