Low Anterior Resection and Total Mesorectal Excision/Coloanal Anastomosis: Open Technique

TECHNIQUES

LOW ANTERIOR RECTAL RESECTION WITH TOTAL MESORECTAL EXCISION

Incision, Abdominal Exploration, and Retraction of the Small Bowel

■ A laparotomy incision is made from the supraumbilical midline to the pubic bone. The fascia is opened between the rectus muscles. As the incision is opened to the level of the pubic bone, the bladder is mobilized to the left of the incision.

■ A careful exploration of the abdominal and pelvic cavity is undertaken to assess for distant metastatic disease and/or unresectable local disease. Attention should be given to the liver, retroperitoneum, aortic and external iliac lymph nodes, as well as peritoneal surfaces. Locally advanced disease may require a diverting colostomy followed by chemotherapy and radiation prior to resection.

■ A fixed abdominal retractor, such as a Bookwalter or Thompson retractor, is used for exposure. A laparotomy pad wrapped around the small intestine from the ligament of Treitz to the terminal ileum will prevent loops of small intestine from migrating into the operative field. A midline incision that barely extends above the umbilicus allows for tacking the small bowel under the right abdominal wall.

Mobilization of the Left and Sigmoid Colon, Colonic Mesentery, and Splenic Flexure

■ The left colon lateral attachments are incised with a cephalad direction. The areolar plane between the left colonic mesentery and the retroperitoneum is identified and opened. This plane is a few millimeters medial from the peritoneal reflection or white line of Toldt. Developing a plane at the exact edge of the white line of Toldt has the potential of lifting the retroperitoneal structures with subsequent ureteral and nerve injury.

■ The splenocolic, phrenocolic, and renocolic attachments are divided at the splenic flexure. In patients with difficult visualization, the transverse colon is retracted downward and the lesser sac is entered over the midtransverse colon by incising the gastrocolic ligament. Development of this plane in a medial to left lateral direction detaches the omentum from the distal transverse colon so that the medial and lateral planes of dissection can be joined to complete the splenic flexure mobilization (FIG 2).

■ The splenic flexure and proximal left colon mesentery are separated from the Gerota’s fascia. Incomplete mobilization of the splenic flexure results in a short colonic conduit and tension on the colorectal anastomosis, which could then lead to a postoperative anastomotic leak.

Vessel Ligation and Left Ureter Identification

■ The separation of the left and sigmoid colon from the retroperitoneum is continued by reversing direction toward the pelvis. The left ureter is identified as it crosses over the left iliac artery and into the pelvis in a way that preserves the retroperitoneal location of the ureter but also identifies the areolar plane that medially extends to the superior hemorrhoidal vessels (SHV) arch (FIG 3). Lifting the mesosigmoid and placing the index finger behind the SHV arch allows the surgeon to incise with electrocautery the right surface of the peritoneum just under the dorsal surface of the SHV. This plane of dissection along the dorsal aspect of the SHV, as it is carried over the promontory, leads into the presacral tissue plane that will be later developed during the TME. At this point, the mesentery is divided in between the sigmoid and descending colon, starting from the antimesenteric border. The SHV are ligated at the level of their origin from the inferior mesenteric artery (IMA) in order to preserve the left colic pedicle intact. The colon itself is not divided. This prevents the colon from dropping into the dissection field during the operation and also allowing for any blood supply deficiencies in the proximal colon to manifest by the end of the dissection and prior to the anastomosis.

■ In cases of coloanal anastomosis, a high IMA transection at its takeoff from the aorta is usually performed, in an effort to prevent anastomotic tension (FIG 4). The collateral marginal artery that connects the middle colic artery and the IMA and runs close to the colon provides blood supply to the distal descending colon in these cases.

■ Reidentification of the ureter prior to IMA or SHV pedicle ligation ensures the left ureter is safe from injury.

■ Additional length of the colonic conduit can be achieved by ligating the inferior mesenteric vein just lateral to the ligament of Treitz.

Posterior Mobilization of the Rectum and Hypogastric Nerve Identification

■ A lighted St. Mark’s retractor is placed posteriorly to the ligated SHV. By retracting the rectum anteriorly, the presacral areolar space is exposed and divided with electrocautery. The hypogastric nerves are identifiable at this location prior to dissecting the presacral space (FIG 5). These nerves should be swept posteriorly and preserved as they course in a medial to lateral direction along the presacral fascia.

■ The presacral dissection plane is bloodless. Proper retraction with the St. Mark’s retractor assists the surgeon in following the areolar plane between the fascia propria anteriorly and the presacral fascia posteriorly, down to the levator muscles and pelvic floor (FIG 6).

■ Failure to properly expose the presacral space with the lighted St. Mark’s retractor risks dissecting to far posteriorly and into the presacral venous plexus. Staying on the anterior surface of the areolar plane close to the mesorectal boundary will allow the surgeon to stay in the presacral space, thus avoiding catastrophic bleeding from injured presacral veins.

■ Blunt dissection should be avoided at all cause, because it can lead to violation of the mesorectum with the attendant increased risk of locoregional tumor recurrence. It is imperative to adhere to a sharp dissection technique when dissecting around the mesorectum.

■ As the posterior dissection continues laterally, the surgeon must proceed on an anterolateral direction, or in a semicircular fashion, to open the lateral planes. This helps avoiding penetrating through the endopelvic fascia, which holds the hypogastric vein and its branches as well as the parasympathetic plexus attached to the lateral pelvic walls. In this fashion, potentially catastrophic bleeding and severe autonomic dysfunction can be averted.

Division of Lateral Ligaments

■ The lateral rectal ligaments can be taken with cautery or with an energy device. It is not usually necessary to ligate vessels within the lateral stalks with the exception of the middle rectal vessel variants. Identification of the lateral rectal ligaments is achieved by placing the rectum on posterolateral traction between the index and middle fingers in the direction opposite of the lateral rectal ligament to be transected (FIG 7).

Anterior Mobilization of the Rectum and Proximal Colonic Transection

■ Following the areolar tissue circumferentially around the rectum and incising the anterior peritoneal reflection connects the right and left lateral dissections. Once the peritoneal reflection is incised, the dissection continues behind Denonvilliers’ fascia, which covers the seminal vesicles and prostate (FIG 7

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