The surgeon now grasps the rectosigmoid junction with his left-hand instrument and draws it to the patient’s right side. This allows the lateral attachments of the sigmoid colon to be seen and divided using cautery. Bruising can usually be seen in this area from the previous retroperitoneal mobilization of the colon from the medial to lateral dissection. Dissection now continues 1 mm medial to the white line of Toldt, toward the splenic flexure. As the dissection continues, the surgeon’s left-hand instrument needs to be gradually moved up along the descending colon to keep the lateral attachments under tension (Fig. 4.7). In this way, the lateral and any remaining posterior attachments are freed, making the left colon and sigmoid into a midline structure (Fig. 4.8). Elevating the descending colon and drawing it medially is useful, as this keeps small bowel loops out of the way of the dissecting instrument and facilitates the dissection. In some patients, particularly very obese or otherwise large patients, it is difficult to reach high enough through the right lower quadrant port. For this reason, the surgeon positions himself/herself between the patient’s legs and the surgeon’s right-hand instrument is moved to the left mid-quadrant port site. This permits greater reach along the descending colon.

Complete lateral mobilization of the left colon up to the splenic flexure is performed as the initial step. The descending colon is pulled medially using an atraumatic bowel grasper in the right lower quadrant port and the scissors are placed in the left mid-quadrant port. A 5-mm left upper quadrant port may be necessary, particularly in those with a very high splenic flexure or very tall or obese individuals. Having freed the lateral attachments of the colon, it is necessary to move medially and enter the lesser sac. Some surgeons prefer to perform this as an initial step before lateral mobilization. To enter the lesser sac, the patient is tilted to a slight reverse Trendelenburg position. The assistant holds up the greater omentum, toward its left side, like a cape. The surgeon grasps the transverse colon toward the left side using a grasper in the right lower quadrant port to aid identification of the avascular plane between the greater omentum and the transverse mesocolon. Electrocautery scissors are used via the left mid-quadrant port to dissect this plane and enter the lesser sac. The surgeon may move to stand between the patient’s legs for this part of the procedure. This dissection is continued toward the splenic flexure. Following separation of the omentum off the left side of the transverse colon, connecting this dissection to the lateral dissection allows the splenic flexure to be fully mobilized (Figs. 4.9 and 4.10). The colon at the flexure is retracted caudally and medially and any residual restraining attachments divided, bringing the entire left colon to the midline.

The patient is returned to Trendelenburg position and the small bowel reflected cranially. The rectosigmoid junction is elevated away from the sacral promontory by the assistant in the left mid-quadrant port, to enable entry into the presacral space. An open atraumatic grasper is used through the right upper quadrant port as if mimicking the role of the St. Mark’s retractor in an open pelvic dissection (Fig. 4.11). The posterior aspect of the mesorectum is identified and the mesorectal plane dissected with cautery scissors, preserving the hypogastric nerves as they pass down into the pelvis anterior to the sacrum. Dissection continues down the presacral space in this avascular, loose areolar plane toward the pelvic floor (Fig. 4.12). Attention is now switched to the peritoneum on the right side of the rectum. This is divided to the level of the seminal vesicles or rectovaginal septum. This is repeated on the peritoneum on the left side of the rectum. This facilitates further posterior dissection along the back of the mesorectum down to the anal canal. For a low anterior resection, it is necessary to perform a total mesorectal excision, and hence the rectum must be dissected down to the muscle tube of the rectum below the inferior extent of the mesorectum. In many cases, particularly those who are obese, or men with a narrow pelvis, some or all of the anterior and lateral dissection must be completed to get adequate visualization to complete the posterior dissection. An atraumatic bowel grasper via the left mid-quadrant port is used to retract the peritoneum anterior to the rectum forward. The peritoneal dissection is continued from the free edge of the lateral peritoneal dissection anteriorly. Lateral dissection is continued on both sides of the rectum and is extended anterior to the rectum, posterior to Denonvilliers’ fascia in most cases, separating the posterior vaginal wall from the anterior wall of the rectum or down behind the prostate in a male patient. The difficulty of dissection will vary depending on the body habitus of the patient, the diameter of the pelvis, and the size and level of the tumor. Rectal mobilization can be very difficult to perform laparoscopically under specific circumstances. Low bulky rectal tumors in the anterior position, morbidly obese men, or tumors adherent to the posterior wall of the vagina may need to be completed in an open fashion via a lower midline or a Pfannenstiel incision. In fact, many surgeons perform much of the pelvic dissection in an open fashion using a hybrid or hand-assisted approach.

Prior to rectal transection, the surgeon must ensure that their distal margin is adequate. Ideally a 2-cm margin is obtained, but recent data suggests that 1-cm or negative distal margin may be acceptable in tumors without high-risk features [7]. A 12-mm port can be inserted through the planned ileostomy site for a very low tumor or the 5-mm right lower port can be increased to a 12 mm for a proximal lesion (Fig. 4.13). The lower rectum may be divided with a stapler either laparoscopically or via an open approach depending on ease of access related to the size of the pelvis. The reticulating stapler is inserted through the 12-mm port, and two to three firings of the stapler are usually required to divide the rectum (Fig. 4.14). A thick tissue and short load are required to fit low in the pelvis (Fig. 4.15). There is no residual mesorectum to divide at this level (Fig. 4.16). Digital examination is performed to confirm the location of the distal staple line, and if there is any doubt about adequacy of the distal margin, a rigid proctoscopy is performed. It is sometimes impossible to divide the rectum laparoscopically as the angulation of the endovascular stapler is limited to 45°, necessitating open division of the rectum or multiple firings. In some patients getting an assistant to push-up on the perineum with their hand may lift the pelvic floor enough to get the first cartridge of the stapler low enough. In some cases placing a suprapubic port allows easier access with the stapler to allow division of the rectum from a top-down approach, perpendicular to the rectal tube.