Low Anterior Resection: Unique Considerations and Optimal Setup


Fig. 24.1

Port setup for Si (and X) system. R1-robotic dissecting instrument, CP-12 mm camera port (8 mm in X system), R2-micro-retracting bipolar grasper, R3-macro-retracting grasper; assistant ports (5 mm or 6 mm AirSeal®, Conmed System, Utica, NY, USA)



When using the Xi system, the cart can be brought from either side with the exception of the right upper quadrant, which is reserved for the bedside assistant. A rotating boom of the Xi system allows the arms to be directed toward the left abdomen and pelvis.


Port Placement


Standard principles of safe port placement should be respected. These include ensuring the appropriate distance between the ports and depth of port insertion. In cases of insufficient instrument reach, which may be encountered during deep pelvic dissection, the ports and the robotic arms may need to be pushed deeper beyond the black line marked on the port’s cannula. Additionally, attention should be given to the position of the robotic base (Si or X system) or the center of the rotating boom (Xi system) in relation to the ports. The shorter distance between the ports and the abovementioned central parts of the robotic system can result in cramming of the external arms, with the possibility of external arm collision. The longer distance would result in decreased reach of the instruments. During the learning curve, it is recommended that the robotic ports be placed in the most optimal location with no regard for a future ileostomy site, or even the extraction site. With time and experience, the ileostomy site and the extraction incision can be incorporated into the port placement.


There are many possible ways to achieve successful port placement . There are, however, differences between the Si and Xi systems in terms of port setup. Overall, the Xi system provides a wider reach of the arms with less chance for external collisions. The Si (or X) system will typically require redocking of the robot in order to complete the left colon mobilization and perform the TME. The techniques for a completely rLAR with the Si (or X) system have been described; however , the authors suggest using them only after obtaining sufficient experience with the simpler techniques [14, 15, 19].


Robotic LAR with the Si System


The technique is based on the hybrid robotic-laparoscopic technique. The robot is used for left lower quadrant dissection, inferior mesenteric artery (IMA) control, and TME. Standard laparoscopy is used for inferior mesenteric vein (IMV) control and splenic flexure takedown. In this technique, a 12 mm camera port is placed at the umbilicus, and an 8 mm robotic port (R1) is placed in the right lower quadrant, one third to one half of the distance from the anterior superior iliac spine to the umbilicus. Two 5 mm assistant ports (a1 and a2) are inserted in the right upper quadrant with a1 placed just cephalad from the horizontal umbilical line in between the camera port and R1 and a2 placed suprapubic on the line of the future extraction port via the Pfannenstiel incision. This four-port configuration should be sufficient for laparoscopic splenic flexure takedown and IMV control. Two additional robotic ports are necessary for the robotic portion. The R3 is an 8 mm robotic port placed above the horizontal umbilical line, on the intersection with the anterior axillary line. An 8 mm R2 is then placed in between R3 and the camera port (Fig. 24.2).

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Fig. 24.2

Port setup for Xi system . X1-macro-retracting grasper for pelvic dissection, X2-micro-retracting bipolar grasper for pelvic dissection, X3–8 mm camera port, X4-robotic dissecting instrument; assistant ports (5 mm, 6 mm AirSeal®, Conmed System, Utica, NY, USA)


During the robotic part of the procedure , R1 is used for a monopolar cautery hook or hot shears, which are assigned to the right hand of the operator. The R2 port accommodates a bipolar grasper-type instrument, and R3 is used for a Cadiere-type (no cautery) grasper. Both R2 and R3 ports are assigned to the left hand of the operator. The R3 instrument is primarily responsible for stationary retraction (macroretraction) of the rectosigmoid during posterior rectal mobilization. It is also used to retract anterior pelvic structures during anterior rectal mobilization. The left hand of the assistant (a1) controls a grasper and helps with macro- and microretraction, while the right assistant hand (a2) is supplied with a suction irrigator in order to actively evacuate the plume and fluid from the pelvis and to assist with retraction and exposure. Zero-degree or 30-degree down camera is used for most of the procedure.


Robotic LAR with This Xi System


The Xi system differentiates from the Si system by its central rotating boom and a reverse numbering of the arms from the left to right. The 8 mm Xi camera can be placed in any robotic port. The ports are placed in an almost linear configuration from the right lower quadrant (one third to one half of the distance between the anterior superior iliac spine and the umbilicus) to the left upper quadrant mid-costal region (Fig. 24.3). Subsequently, the 8 mm camera port (X3) and two additional robotic ports (X2 and X1) are placed on that line, evenly distributed. Frequently, the camera port (X3) corresponds with the umbilicus, which is the preferred site for the camera. The line for the port positions can be modified by pivoting it around the X4 port (which is constant). A more vertical port placement line brings the X1 closer to the midline and allows for more comfortable dissection around the splenic flexure and the left colon. A rotation of the port placement line in a more horizontal direction allows for more comfortable pelvic dissection and with better reach of the X1 and X2 instruments into the deep pelvis. The assistant port configuration includes two ports in the right upper quadrant or one port in that location and the other one in the suprapubic location. Alternatively, the entire robotic port line, including the X4 port, may be moved in parallel toward the right upper quadrant.

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Fig. 24.3

Robotic cart positioning


The assignment of the arms for the pelvic dissection is essentially the same as in the Si technique, but for the splenic flexure mobilization, the instruments can be rearranged, including the 8 mm camera, which can be placed in any robotic port. If the assistant port is chosen to be placed in the suprapubic location, the right hand of the assistant will have to be inserted between the robotic arm of the right lower quadrant (R1 or X4) and the camera arm. This maneuver is not usually problematic; however, the assistant should be alert for any sudden swings of the nearby robotic arms.


Once the rectal mobilization is complete , a robotic stapler is typically introduced via the right lower quadrant port (R1 or X4), after upsizing of that port with a 12 mm designated stapler port.


The X system utilizes the Xi system ports and instruments, but the port placement can be chosen between Si and Xi.


Extraction Site


The preferred extraction site is a Pfannenstiel incision for cosmetic reasons and an extremely low hernia formation rate [20]. Alternatively, the specimen can be extracted through the ileostomy site. In this case, the incision would likely have to be enlarged at the skin and fascial levels for the larger specimens. This could increase the risk of stomal prolapse and/or parastomal hernia. Select patients can undergo transanal or transvaginal specimen extraction, particularly when hand-sewn anastomosis follows the pull-through procedure [21].


Operative Technique: Surgical Steps


After safely establishing the pneumoperitoneum, diagnostic laparoscopy is carried out to confirm the appropriateness of the planned resection, including plans for splenic flexure release and use of a hybrid or fully robotic technique.


Exposure of the base of the left colon mesentery and the sacral promontory is obtained by adjusting the table tilt and sweeping of the small bowel to the right and upper abdomen. All necessary ports are then placed, the robot docked, and the instruments inserted under direct vision.


A decision is made regarding where to initiate the dissection and the sequence of dissection. Most surgeons prefer a medial to lateral approach for mesenteric dissection. However, the surgeon should be familiar with the lateral to medial approach if exposure of the base of the mesentery is complicated by severe visceral obesity or inability to sweep away small bowel loops, uncertainty regarding the anatomy, aneurysmal aorta, suspiciously enlarged lymph nodes, or extensive scarring or inflammation. The medial to lateral approach can be initiated by incising below the IMV, above or below the IMA, or at the level of the sacral promontory. Likewise, the splenic flexure can be mobilized using a lateral to medial, supra-mesocolic or infra-mesocolic approach.


Mesenteric Dissection and IMA Ligation


When starting the dissection below the IMV or above the IMA, the peritoneal incision should be initiated between the vein and a distinct autonomic (sympathetic) nerve running along the left side of the aortic surface. This nerve, which serves as a very helpful anatomical landmark, eventually joins the (peri) IMA nerve plexus. A proper initial incision guarantees easiest access to the correct plane within lamellar Toldt’s fascia, between the retroperitoneal and the mesocolic fascia [22]. Squiggly vessels of Toldt’s fascia , left on the mesocolic side of the dissection, indicate that the dissection was carried out too deep. Small oozing from these vessels can eventually stain the dissection plane. A proper (non-bloody) dissection plane should keep the squiggly vessels on the retroperitoneal side.


When the dissection is initiated below the IMA , it is more difficult to find the proper plane (Toldt’s fascia ). This almost always leads to dissection in the deeper plane, below the retroperitoneal fascia. The main reason for this difficulty is the presence of a distinct autonomic nerve layer in front of the aorta, in addition to often seen fibrosis, inflammation, and sometimes lymphadenopathy between the IMA and the aorta. The main consequence of too deep of a dissection is oozing from the small vessels and potential injury to the ureter and the gonadal vessels.


For the reasons stated above, the dissection is frequently initiated at the level of the sacral promontory. This is done by retracting the rectosigmoid, with the far-left instrument stretching the peritoneum at the base of the rectosigmoid. Hot dissection also helps in plane identification between the mesentery and the prehypogastric nerve fascia (pHGNF) . The latter is a fascial layer covering the superior hypogastric plexus (below the aortic bifurcation), both hypogastric nerves , and the sacral splanchnic nerves (SSN) deeper in the pelvis (Fig. 24.4) [23]. The pHGNF must be kept intact in order to minimize injury to these important autonomic nerves.

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Fig. 24.4

Prehypogastric nerve fascia (pHGNF ) covering the superior hypogastric plexus and both hypogastric nerves. The fascia was incised between both diverging nerves, and the plane of dissection was changed, leaving the pHGNF attached to the mesorectum


Dissection is continued cephalad along and above the nerves and pHGNF layer, toward the root of the IMA , avoiding further lateral dissection. A helpful maneuver at this point involves moving the dissection above the IMA. This helps to establish a proper layer of easily identifiable Toldt’s fascia above (cephalad from) the IMA. In addition, “connecting the dots” between the planes above and below (cephalad and caudal of) the IMA helps prevent violation of the retroperitoneal fascia along the entire length of dissection. Thus, if the retroperitoneal fascia remains intact in a bloodless operating field, the left ureter and gonadal vessels will also be left intact below the fascia, and a search for the ureter by dissection through the retroperitoneal fascia will not be necessary. Conversely, if the operating field becomes bloody and/or the retroperitoneal fascia is violated, the ureter must be clearly identified.


Dissection continues at the root of the IMA , where it is circumferentially dissected, isolated, and then divided. Several methods can be used, including the laparoscopic or robotic clip applier (most cost effective), a robotic vessel sealer, a vascular stapler, or a laparoscopic bipolar energy device. The dissection is then carried from the medial to the lateral aspect by dissecting between the retroperitoneal and mesocolic fascia. One of the robotic arms, usually the far-left one, provides a macroretraction to the detached mesenteric base and should be continually adjusted to provide adequate tension during medial to lateral dissection. The dissection is extended onto the white line of Toldt. Any difficulty encountered during medial to lateral dissection, such as difficulties identifying the correct plane or the left ureter, can be circumnavigated by changing the dissection to the lateral to medial approach. When the lateral to medial dissection is performed, the far-left robotic arm is applied laterally to the white line of Toldt. The other retracting arm provides the medial microretraction on the bowel and mesentery.


Splenic Flexure Release


The various strategies for laparoscopic splenic flexure release (SFR) are described in the Masters chapter (Chap. 4) on laparoscopic SFR, tips and tricks. Robotic surgeons should be familiar with the lateral to medial, supra-mesocolic or infra-mesocolic approach, in case difficulties arise and an alternative approach is needed. Several techniques of splenic flexure mobilization have been described for both the Si and Xi systems [14, 15, 24]. While it is possible to mobilize the flexure and perform the TME with one robotic setup, the Si system techniques are generally more demanding. They frequently require arm repositioning and/or system redocking and may be achieved easier with the hybrid (laparoscopic) approach. On the other hand, the design of the Xi system allows for less external arm collisions and better reach. When combined with integrated table motion and appropriate port placement, it allows for more effective one port setup for splenic flexure mobilization as well as for rectal dissection. Also as mentioned, the in-line port setup must be done in a more vertical fashion, thus opening a more effective angle for the splenic flexure. Alternatively, a completely horizontal, mid-abdominal robotic port placement can effectively serve the splenic flexure and pelvis, following boom rotation and instrument exchange.


Rectal Mobilization


This part of the dissection is fairly standardized and very reproducible with repetitive movements, particularly when compared with splenic flexure mobilization. The objective of successful TME is to perform a gradual release of the mesorectum (posterior, anterior, and both lateral) using effective and atraumatic retraction of the mesorectal specimen.


Posterior Dissection


The rectum is mobilized posteriorly to the level of the lower sacrum. During the upper part of the dissection, care should be taken to preserve the pHGNF (the innermost layer of the presacral (Waldeyer’s fascia). The pHGNF covers the superior hypogastric plexus, the right and left hypogastric nerves, and a significant portion of the sacral splanchnic nerves), all of which are important as safety landmarks and are essential for both sexual and urinary function (Fig. 24.5). Additionally, because the posterior avascular plane can be easily identified, it is often advantageous to continue this plane of dissection around the rectum, mobilizing the mesorectum from the right and left lateral pelvic compartments. In order to provide the best exposure, the far-left robotic arm with Cadiere forceps is used to provide a macroretraction to the rectum in the cephalad and anterior direction. The medial left robotic arm with the fenestrated bipolar grasper is then used to provide a gentle microretraction on the mesorectum, close to the area of hook/scissors dissection (performed with the right arm). In experienced hands, using the wrist of the instrument at a 90-degree angle to the shaft, the macro-retracting arm can frequently lift and support the mesorectum without actually grasping it (Fig. 24.6). Posterior TME dissection proceeds either between the mesorectal fascia and the pHGNF (with reduced risk of injury to the nerves) or between the pHGNF and the nerves, which exposes the nerves but may extend the posterior resection margin in cases where the mesorectal fascia is threatened by tumor. It is the authors’ preference to preserve the pHGNF until a clear divergence of the two hypogastric nerves can be seen toward both pelvic sidewalls. At that point, the pHGNF is routinely incised, and dissection falls into the plane between the pHGNF and the sacral splanchnic nerves (Fig. 24.4).

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Fig. 24.5

Sacral splanchnic nerves (SSN) originating from the pelvic sympathetic trunks and converging in the pelvic plexus (seen in the left upper corner); pHGNF lifted with the mesorectum


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Fig. 24.6

Retraction of the mesorectum during posterior dissection , left hand grasper with 90-degree wrist angulation


Another implication of precise and bloodless surgery is the ability to visualize anatomical landmarks to guide the dissection . This is important in the case of unclear anatomy due to inflammation, tumor, previous radiation, or previous dissection. While it is rare to visualize SSN during open surgery, they are easily identified during robotic surgery and should be preserved (Fig. 24.5).


It is also important to point out that many general surgery and colorectal textbooks describe Waldeyer’s fascia as a structure penetrating the mesorectum and spreading between the sacrum and the rectal tube. It is often referred to as “rectosacral” or “retrosacral.” In fact, the presacral Waldeyer’s fascia has two components, with a more posterior one covering the presacral vessels and a more superficial one covering the hypogastric and sacral splanchnic nerves. The name of the latter layer is the pHGNF (prehypogastric nerve fascia). Waldeyer’s fascia spreads onto the lateral aspects of the mesorectal compartment, where it ultimately embeds the pelvic (inferior hypogastric) plexi (Fig. 24.7).

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Fig. 24.7

Pelvic fasciae and nerve structures . (Used with permission of Wolters Kluwer from Marecik et al. [25])


Lateral Dissection


The area of the lateral rectal attachments (stalks) is referred to by authors as “lateral tethered surface” and not “lateral ligament.” These are often taken down by cautery and sharp dissection (Fig. 24.8). When most of the lateral mobilization is completed as a continuum of the posterior dissection around the rectum, this part of the dissection is relatively easy, particularly if the line of anterior dissection has been previously marked (Fig. 24.9). Care should be taken, however, not to injure the lateral pelvic plexi. This is where the sympathetic hypogastric nerves and sacral splanchnic nerves converge with the parasympathetic sacral pelvic nerves (known as nervi erigentes , located in the posterior aspect of the lateral compartment) (Fig. 24.7) [25]. The left lateral dissection is performed with the far-left instrument retracting the lateral wall, the medial left instrument pushing the mesorectum to the right, and the right-hand instrument crossing the medial left instrument for dissection. The right lateral dissection is performed with the far-left instrument retracting the mesorectum (macroretraction to the left), while the medial left instrument pushes the right anterior Denonvilliers’ fascia (DF), or the lateral wall, while positioned in front of or behind the right-hand dissecting instrument.

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May 2, 2020 | Posted by in GASTOINESTINAL SURGERY | Comments Off on Low Anterior Resection: Unique Considerations and Optimal Setup
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