The peritoneum over the region of the left kidney is divided as gentle traction is maintained downward and medially on the splenic flexure of the colon. There is a tendency to grasp the colon and to encircle it completely with the fingers. This tends to puncture the thinned out mesentery. Rents can be avoided if a gauze pack is used to gently sweep the splenic flexure downward and medially (Figure 6). Usually, it is unnecessary to divide and ligate any vessels during this procedure. The peritoneum in the left lumbar gutter is divided, and the entire descending colon is swept medially.
The rectosigmoid is freed from the hollow of the sacrum as shown in Plates 70 and 71, Total Mesorectal Excision. The sigmoid is first separated from any attachments to the iliac fossa on the left side, and the left gonadal vessels and the ureter are identified throughout their course in the field of operation (Figure 7). Often, especially in the female, a very low-lying lesion can be mobilized and lifted up well into the wound.
After the bowel has been freed from the hollow of the sacrum, the fingers of the left hand should separate the right ureter from the overlying peritoneum by blunt dissection (Figure 8). The peritoneum is incised some distance from the tumor, and the rectum is freed further down to the region of the levator muscles using the mesorectal dissection (Plates 70 and 71). Division of the middle hemorrhoidal vessels with the suspensory ligaments may be necessary to ensure the needed length of bowel to be resected below the tumor. The surgeon should not hesitate to divide the peritoneal attachments in the region of the pouch of Douglas, to free the rectum from the prostate gland in the male and from the posterior wall of the vagina in the female. The inferior mesenteric artery is freed from the underlying aorta to near its point of origin (Figure 9). Three curved clamps are applied to the inferior mesenteric artery, and the vessel is divided and ligated with 00 silk. The inferior mesenteric vein should be ligated at this time, before the tumor has been palpated and compressed due to the manipulation required during resection.