Dissection and Detachment of the Rectosigmoid Colon

The initial step in this technique is dissection and detachment of the distal sigmoid colon and the rectum. This can be performed from either the lateral side or the medial side of the rectosigmoid (Figure 8.5.3). When the lateral approach is used, the dissection plane can be naturally exposed while the descending colon is being dissected if the operating table is tilted with the right side down. Ureter and gonadal arteries/ veins are dissected without any damage if Toldt's fusion fascia, con-

Figure 8.5.3. Dissecting plane from the medial or lateral sides of the sigmoid colon optimally involve sweeping the Toldt's fascia posteriorly (thick gray line). This safely isolates and preserves the ureter and gonadal vessels.

White Line Toldt

Figure 8.5.3. Dissecting plane from the medial or lateral sides of the sigmoid colon optimally involve sweeping the Toldt's fascia posteriorly (thick gray line). This safely isolates and preserves the ureter and gonadal vessels.

Toldt's fascia

nected to the anterior layer of the Gerota's fascia, is exposed and the dissection performed in front of this fascia.

With the medial approach, the superior rectal arteries/veins are carefully grasped initially and lifted up ventrally along with the mesentery. Next, an incision is made in the anterior layer of the mesentery, and blunt dissection is performed between the vessels and the retroperito-neum, encountering the ventral side of Toldt's fusion fascia (Figure 8.5.4). It is always an option to perform dissection from the lateral side later, if the ureter and gonadal arteries/veins are verified and dissected on their dorsal side, also exposing the psoas muscle (Figure 8.5.5).

By introducing grasping forceps from the left lower quadrant, after detachment of adhesions at the S-D (sigmoid descending) colon junction, we next identify the Toldt's fusion fascia. It will be better not to dissect too deeply at the S-D junction, only to detach adhesions. The "white line" should be incised and the descending colon should be dissected just anterior to Toldt's fusion fascia. The assistant should introduce the intestinal grasping forceps with gauze from the left lower quadrant cannula to help confirm the proper plane. We take care at this point to not grasp the colon itself, but to attempt to hold the mesentery or an epiploic appendage.

It may be easiest to identify the gonadal vessels and ureter just beneath Toldt's fusion fascia, and this is acceptable if necessary to be sure these structures are protected (Figure 8.5.5). However, if dissection

White Line Toldt
Figure 8.5.4. In the medial approach, the superior rectal (or inferior mesenteric) vessels are tented anteriorly and the plane is dissected between the vessels and Toldt's fascia.
Detched Rectum

Figure 8.5.5. It is always an option to perform dissection laterally, verifying the location of the ureter and gonadal vessels.

may proceed safely just anterior to Toldt's fascia, bleeding is kept to a minimum. When arrest of bleeding is needed, we avoid irrigating with saline, and keep the plane dry by wiping the area with a small gauze introduced through the left lower quadrant cannula.

In the dissection just medial to the ureter, appreciating Toldt's fusion fascia can help to identify the anterior surface of the superior hypogas-tric plexus, most prominent toward the midline. Another helpful anatomic point is that the site where ureter and gonadal vein crosses is approximately the same anatomic level as the root of the inferior mes-enteric artery.

The superior rectal artery and vein are delineated by retracting the mesentery of the sigmoid colon to the left and slightly ventrally (by the assistant), with forceps introduced from the cannulae of the left side and the suprapubic region. Then, a window is created just to the left of the pedicle using blunt dissection, so that the pedicle is dissected both medially and laterally. We then apply a small retractor through the left upper quadrant cannula to the window of the mesentery, drawing the pedicle ventrally, and dilate the window in a cephalocau-dal manner using the forceps and electrosurgery.

Division of the Vessels

Around the root of the inferior mesenteric artery (IMA), the lumbar splanchnic nerves and lymphatic vessels arise from the right and left sides of the aorta, making the tissue in this area thick. Bleeding tends to occur readily with dissection. Thus, step by step careful dissection is required using the dissecting forceps and scissors. Exposing the root of the IMA carefully, it is possible to preserve the nerves using either electrosurgery or the Laparoscopic Coagulating Shears (LCS) (Harmonic Scalpel; Ethicon Endosurgery, Cincinnati, OH). Once the adventitious tunica of IMA is exposed, we separate it sufficiently around the vessels to perform clipping, then transection (Figure 8.5.6). We take care to only divide the nerves that branch toward the sigmoid colon by LCS, so as not to injure the aortic nerve plexus itself, especially on the left side, and furthermore, we take care to also protect the nerve bundle around the IMA on the cephalic side. After sweeping the pedicle free from the retroperitoneal structures, we then resect en masse the inferior mesenteric vein (IMV) and the left colic artery by stapling devices or LCS from the right-sided cannulae. If the instrument is introduced from the suprapubic port, the angle becomes too tangential to the vessels, leading to difficulty in proper alignment with the vessel. Thus, the pedicle of the IMV and left colic should be divided from the right-sided cannulae. We take care to identify the ureter and gonadal vessels one more time before dividing any tissues (Figure 8.5.7).

If the tumor is located in the lower rectum or if it is a T1 rectosigmoid cancer, the mesentery can be divided more distally, e.g., between the left colic artery and the first sigmoid colon artery. Then by using traction from a grasper in the left lower quadrant, by pulling the mesentery

Rectosigmoid Arteries

Figure 8.5.6. Once the adventitious tunica of the inferior mesenteric artery is exposed, we clip then transect it. Hypogastric nerves are exposed and preserved.

Toldt Fascia
Figure 8.5.7. Next, the inferior mesenteric vein and the left colic artery can be simultaneously divided with an endoscopic stapler from the right side. Note that the ureter and gonadal vessels are clear of the stapler.

cephalad, the superior rectal artery and vein may be resected/divided using a vascular endoscopic stapler.

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Responses

  • arianna
    What is a detached colon?
    5 years ago

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