How is the sigmoid colon mobilized during laparoscopic left hemicolectomy?

Updated: Apr 13, 2020
  • Author: David B Stewart, Sr, MD, FACS, FASCRS; Chief Editor: Vikram Kate, MBBS, MS, PhD, FRCS, FACS, FACG, FRCS(Edin), FRCS(Glasg), FIMSA, MAMS, MASCRS, FFST(Ed)  more...
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The patient is positioned as previously described (see Patient Preparation). Whether a lateral-to-medial (LTM) or a medial-to-lateral (MTL) approach is used is a matter of preference. The most important feature of colon mobilization is identification of the interface between the colonic mesentery and the retroperitoneum. This tissue interface is not the white line of Toldt, though the Toldt line must be incised to expose the mesocolon-retroperitoneum interface.

The author prefers an MTL approach (see the video below), for several reasons. This approach brings the inferior mesenteric artery (IMA) immediately into view, as well as two avascular mesenteric windows, which are always present immediately cephalad and caudal to the IMA. In addition, it requires only one retracting instrument, which facilitates single-site surgery, and it does not require looking "over" the colon from the patient’s right side, thereby allowing less vigorous retraction of the colon and creating less of an opportunity for injury to the specimen.

Laparoscopic left colectomy. Approach to medial-to-lateral mobilization of sigmoid colon, with ligation of inferior mesenteric artery and identification of left ureter.

The mesentery can be easily scored along its medial aspect either mechanically or with a cautery, and the sigmoid mesentery can be retracted away from the retroperitoneum while an energy device is used to perform a blunt and bloodless tissue distraction that involves elevating the mesentery en bloc away from the retroperitoneum.

This technique can also minimize the extent to which tissue is grasped and exposed to electrical energy, until such time as the left ureter is exposed. The retracting instrument can be inserted into the plane between the mesentery and the retroperitoneum, lifting the mesentery toward the anterior abdominal wall without grasping and tearing tissue.

The IMA is circumferentially isolated to ensure that the left ureter is not inadvertently transected or thermally injured. The left ureter and IMA are, in the native anatomy, immediately adjacent, with the vessel lying over the ureter. For this reason, as well as both to allow a complete mobilization of the sigmoid colon and to achieve an adequate lymph node yield in cases of cancer, the sigmoid colon is completely mobilized to the midline of the peritoneal cavity.

With the IMA skeletonized and with the colon mobilized so that the colon can be retracted straight toward the anterior abdominal wall, the left ureter can easily be located from both a medial and a lateral view. These points should be documented in the operative report, describing the care taken to identify and protect the left ureter. If these steps cannot be achieved, the IMA should not be blindly ligated, and the procedure should be preemptively converted to laparotomy for the patient’s safety.

For colonic malignancies, the IMA should be ligated proximal to its bifurcation to remove the entire lymph node cache by transecting the artery near its junction with the aorta. Conversely, for benign diseases, the IMA may be ligated more distally so as to reduce the risk of urinary and sexual dysfunction from damage to the autonomic nerves in the para-aortic region.

Even in the setting of benign disease, by ligating the IMA at the level of its bifurcation and using a more proximal level of mesenteric transection, fewer second- and third-order arterial vessels are encountered, which reduces the risk of pesky bleeding because a more proximal mesocolic dissection involves bloodless planes between named vessels.

This technique also removes diseased and thickened mesentery that must be maneuvered over or around in constructing a tension-free colorectal anastomosis. Furthermore, mobilizing the colon in this manner, where the mesentery is freed from the retroperitoneum at the midline peritoneal cavity, allows full exposure and isolation of the left ureter and kidney, prevents devascularization of the colon through distal transection of its mesentery, and provides maximal colonic length for a proper anastomosis.

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