How is the colon mobilized during total mesorectal excision (TME)?

Updated: Feb 16, 2021
  • Author: Nanda Kishore Maroju, MRCS, MS, MBBS, DNB; Chief Editor: Kurt E Roberts, MD  more...
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Answer

This step involves mobilizing the sigmoid colon, the left colon, and the splenic flexure. At the end of a properly performed mobilization, the colon from the sigmoid to the transverse colon can be lifted freely towards the right side, up to the midline. The purpose of this step is to ensure a tension-free anastomosis between the colon and the rectum during reconstruction.

Conventionally, the sigmoid colon is mobilized first from the left. Adhesions between the sigmoid and the lateral abdominal wall must be divided before the line of peritoneal reflection can be identified and divided. Once the sigmoid is stood up to its full length at the apex, the peritoneal reflection is incised just behind the white line.

The surgeon and assistant work in tandem in applying traction and countertraction to demonstrate the correct surgical planes. The left ureter and hypogastric nerves can be demonstrated overlying the bifurcation of the common iliac artery at the base of the sigmoid mesentery (the apex of the V formed by the sigmoid mesocolon). These are swept laterally and dissection proceeds inferiorly, towards the sacral promontory in a plane anterior to the nerves.

The surgeon, in creating this plane, will push down the nerves onto the pelvic fascia. The appearance of a loose areolar tissue below the level of the promontory confirms the correct plane between the visceral peritoneum and the pelvic fascia. Further rectal mobilization is deferred until later in the operation.

The division of the peritoneal reflection is now taken superiorly to mobilize the left colon. While mobilizing the left colon, an inexperienced surgeon may lose the plane and enter the Gerota fascia. This can be avoided by ensuring a more medial dissection after division of the peritoneal reflection, while keeping the colon lifted anteriorly. The left colon is mobilized until the splenic flexure.

The splenic flexure can be easily brought down by entering the lesser sac after separating the greater omentum from the transverse mesocolon. Often, a difficult splenic flexure mobilization is due to an inadequate incision and therefore inadequate exposure of the flexure.

High ligation of the inferior mesenteric artery, which was earlier considered to be a part of proper oncologic surgery, does not have any proven survival benefit. However, it serves a different but important function in ensuring successful anastomosis. Ligation of the artery at its origin and ligation of the inferior mesenteric vein at the inferior margin of the pancreas increase the mobility of the colon and therefore reduce tension. This technique also serves to preserve the arterial arcade along the colon and again contributes to the survival of the anastomosis.

The surgeon starts from the base of the sigmoid mesocolon again, but on the right side. The peritoneum is divided anterior to the plane of the hypogastric nerves, and the division is taken superiorly in a plane just anterior to the aorta. The inferior mesenteric artery is identified as it takes off from the aorta. It is good technique to dissect out the artery before ligation to avoid injury to the hypogastric nerves. Superior dissection after division of the artery allows identification and division of the inferior mesenteric vein just below the pancreas.

The colon must be divided before one proceeds with rectal mobilization. The level of division is conventionally at the junction of the descending colon and the sigmoid colon. If vascularity is good, division at the midpoint or apex of the sigmoid colon is acceptable as well. It is important to recognize that this step also prepares the proximal component of the anastomosis, and the division of the mesocolon should ensure that the arterial arcade to the colon at the level of division is preserved.

The technique used in dividing the colon is determined by the choice of reconstruction. Stapled division is ideal when a short colonic pouch–rectum anastomosis is considered. For a straight colorectal anastomosis, the proximal and distal divided ends may be tied with purse-string sutures and clamped, respectively, to save on staplers. (See the image below.)

Total mesorectal excision: Mobilization and divisi Total mesorectal excision: Mobilization and division of the colon.

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