Patient Positioning

Patients are placed in a modified lithotomy position to perform a low anterior resection. This allows access to the perineum for a stapled anastomosis. The patient’s arms are usually extended to allow access for the anesthesiologist. In addition, a self-retaining retractor is quite helpful for exposure. Proper positioning of the patient and the retractor is critical to prevent iatrogenic nerve injuries.

Peripheral Nerve Injuries

• Consequence

Clearly, the consequences of this complication depend on the severity of the injury. Most peripheral nerve injuries occur from prolonged compression or stretch. Often, this is just neuropraxis and will resolve completely with time. Less commonly, permanent injury can result that will leave a permanent disability.

Grade 1 complication (if resolves); grade 4 (if permanent)

• Repair

Generally, there is no operative repair for patients with peripheral nerve injury from compression or stretch. Treatment is just supportive, which would include physical and occupational therapy.

• Prevention

Careful patient positioning is key to prevent injuries.⁶ Well-padded stirrups are necessary. The patient’s heel should be placed firmly in the foot of the stirrup so that the weight of the leg is supported by the patient’s heel. It is also helpful to tilt the stirrup posteriorly to prevent pressure from being applied to the posterior and lateral aspects of the lower extremity, which will aid in preventing common peroneal nerve injury. This area can be further padded if necessary. To prevent brachial plexus injuries, the patient’s arms should rest easily and should not be extended more than 90°.⁶ Furthermore, nothing should be placed between the shoulder blades that can stretch the brachial plexus by elevating the chest. The anesthesiologist and operating staff should also monitor the position of the arms because they may shift during the procedure, particularly if the patient is placed in Trendelenburg position to gain additional exposure. Finally, to prevent femoral injuries, great care must be taken when utilizing a self-retaining retractor.⁷ Retractors over the inguinal region should be used with caution, especially in thin patients (Fig. 25-1). However, if necessary, use the most superficial retractor available (e.g., the bladder blade) (Fig. 25-2) because deeper retractors are more likely to compress the femoral nerve, which runs just beneath the psoas muscle. If the operation is prolonged, periodically release and replace the retractors to limit the potential for prolonged compression to an isolated spot. If a perineal approach is necessary at any time, take care to remove the abdominal wall retractors as well. This injury is more common with a transverse incision, which is being utilized more frequently as surgeons adopt a laparoscopy-assisted approach to rectal surgery.

Figure 25-1 Self-retaining retractor. To prevent femoral nerve injury, great care must be used when placing retractor blades (marked with an X) in the inguinal region.

Figure 25-2 Examples of self-retaining retractors. Arrow identifies the retractor with the least depth and, therefore, the least likely to damage the femoral nerve.

Incision

Most low anterior resections can be accomplished through a midline incision. Exposure is critical to safely complete all portions of the procedure. To properly expose the pelvis, the incision frequently needs to go all the way to the pubis. This will allow the best visualization of the deep pelvic structures. For most low anterior resections, complete mobilization of the splenic flexure is also necessary. Therefore, the upper extent of the incision is often well above the umbilicus. In patients who are thin or have a low splenic flexure, the incision may need to extend only to the umbilical region. It is best to start with a lower midline incision and then extend as necessary to gain the required exposure.

Bladder Injury

Although rare, iatrogenic injuries to intra-abdominal structures can occur while the abdomen is being opened. Clearly, these injuries are more likely to occur in patients who have had previous abdominal surgery. However, when doing a low anterior resection, special consideration should be given to the lower portion of the incision. While extending to the pubis, an injury to the dome of the bladder is possible and care must be taken to avoid this problem.

• Consequence

Fortunately, an injury to the bladder while making an incision is usually in the bladder dome. This is generally readily apparent and can be promptly fixed. When this is done, there are few long-term consequences, except for prolonged catheterization. An unrecognized injury will lead to an intra-abdominal urine leak and can result in sepsis. Repair is also greatly complicated and will require long-term bladder drainage.

Grade 2 complication (if recognized); grade 3 complication (if not recognized)

• Repair

The bladder dome is easily repaired and generally forgiving. Closure of the defect is generally done in two layers with an absorbable suture. Permanent suture is avoided to prevent future calculi and granulomas. To keep the bladder decompressed, a Foley catheter is generally kept for approximately 7 to 10 days.⁸

• Prevention

When opening the abdomen, it is important to get all the way to the pubis for proper pelvic exposure. However, most of the benefit is from incising the anterior fascia. The bladder will lie beneath the pyramidalis and rectus muscles. Therefore, if the dissection is always above these muscles, the bladder cannot be injured (Fig. 25-3). Division of the posterior peritoneum is not always necessary in this region because it is easily retracted with a self-retaining retractor. If division of this peritoneum is necessary, it can be done carefully layer by layer to identify the bladder dome. Furthermore, the dissection of the peritoneum can veer a bit off midline, which will help avoid the bladder dome.

Figure 25-3 Opening incision. To avoid bladder injury, incise the anterior fascia all the way to the pubis, staying anterior to the underlying muscle.

Colon Mobilization and Ligation of the Mesenteric Vessels

In order to perform a low anterior resection of the rectum, the sigmoid colon must be fully mobilized. Furthermore, in most instances, complete mobilization of the descending colon and splenic flexure is also required to perform a tension-free anastomosis (see later). Most mishaps that can occur during this portion of the procedure are similar for any left-sided colonic operation and are well described in Chapter 24 (Left Colectomy: Open and Laparoscopic). These complications are briefly reviewed here.

Bleeding

• Consequence

If the proper planes are found and dissected properly, bleeding from colonic mobilization should not be significant. When bleeding is encountered, the surgeon should question whether he or she is in the proper plane and adjust accordingly. Most bleeding is easily controlled without any significant sequelae. Some evidence suggests that patients who get a blood transfusion are more likely to have a cancer recurrence and/or an infectious complication of surgery.^9–11 Whether this is due to the immunosuppression of the transfusion or is just a marker for a difficult case has not been determined.^12,13 Nevertheless, to prevent the unnecessary risk of a blood transfusion, bleeding should be kept to a minimum whenever possible.

Grade 1 complication

• Repair

Identification and ligation are all that is necessary for proper control of bleeding. If necessary, the gonadal vessels can be ligated once the ureter is clearly identified. Bleeding from the major vascular structures, such as the aorta or iliac vessels, is unusual but can be directly repaired after proper proximal and distal control.

• Prevention

Proper identification of the avascular planes is necessary to prevent unnecessary bleeding. The descending colon and its mesentery lie just anterior to the retroperitoneum and its associated structures. An areolar plane exists between the mesocolon and the retroperitoneum and, when dissected, allows the colon and the mesocolon to be fully mobilized to the midline position. The dissection is begun by dividing the lateral peritoneum of the sigmoid and descending colon. Rapid identification of the gonadal vessels can be quite helpful because these vessels are the most anterior of the retroperitoneal structures and should be swept posteriorly off the colonic mesentery (Fig. 25-4). Care must be taken to stay above the gonadal vessels because they are quite fragile and will bleed with too much manipulation. However, when this plane is properly identified, there should be little bleeding; if this plane is followed, the colon and the mesocolon should be lifted off the left kidney to prevent inadvertent kidney mobilization. As the gonadal vessels are swept posteriorly, the mesocolon and, specifically, the inferior mesenteric vessels are elevated to a midline position. The ureter, which passes beneath the gonadal vessels, can be identified as it crosses the iliac vessels. Once the gonadal vessels and kidney have been swept posteriorly, the peritoneum on the right-hand side should be divided just at the sacral promontory and underneath the superior rectal artery. This will allow entrance into the retrorectal space, which is also avascular. This dissection should meet the previous dissection on the left-hand side and create a window under the superior rectal artery (Fig. 25-5). The superior rectal artery can then be further dissected on the right-hand side all the way to the aorta, where it is now the inferior mesenteric artery (IMA). If the dissection on the left-hand side was done properly, the gonadal vessels and ureter should be easily visualized from the right-hand side underneath the IMA. An avascular window can now be identified through the mesocolon on the left-hand side of the IMA. The inferior mesenteric vein (IMV) is just to the left of the IMA and can be dissected out separately. Care should be taken to identify the duodenum, which should be located just superior to the IMA (Fig. 25-6). Once these vessels are properly identified, they can be divided and doubly ligated (Fig. 25-7). It is advisable to leave a stump for the IMA in case vascular control is lost. Reclamping and ligating the base of the IMA is considerably easier than repairing a defect in the aorta. Great care with the IMV is also critical because this vessel is prone to retract underneath the pancreas, which will make vascular control quite difficult once it is lost. This describes a high ligation of the IMA and IMV. From an oncologic perspective, this may not be necessary,¹⁴ and division of the IMA and IMV can be done together with a single clamp just distal to the takeoff of the left colic artery. However, for a very low anastomosis, division of these vessels is often required to provide the necessary colonic length to do a safe, tension-free anastomosis (see the section on “Anastomosis”).

Figure 25-4 Dissection of the gonadal vessels off the mesentery of the colon. This plane is avascular and will guide the surgeon to the plane separating the colon and its mesentery from the retroperitoneum.

Figure 25-5 Mesentery of rectosigmoid colon from the right-hand side. A, Line shows the approximate course of the superior rectal artery. Shaded area represents avascular window posterior to the superior rectal artery at the level of sacral promontory. B, Avascular window is opened, posterior to the superior rectal pedicle.

Figure 25-6 Position of the duodenum in relation to the pedicle of the inferior mesenteric vessels. Yellow shows the approximate location of the inferior mesenteric artery (IMA). Note that the peritoneum to the left of the IMA has been incised and the IMA is being lifted off the aorta by the left dissecting hand.

Figure 25-7 Inferior mesenteric vessels are identified and clamped (A) and then ligated (B). Forceps point to the ureter and the retroperitoneum, which have been swept posteriorly (A). Note the proximity of the ureter to the inferior mesenteric vessels at the point of ligation (B).

Ureteral Injury

An intra-abdominal injury to the ureter is possible when the sigmoid and descending colon is mobilized. This is fully described elsewhere in the text so it is only reviewed here. Clearly, proper identification of the ureter is essential to preventing injuries. The ureter is usually identified as it crosses the iliac vessels but must be followed superiorly and swept posteriorly to prevent injury when ligating the IMA and IMV. It is important to remember that the ureter lies beneath the gonadal vessels, so if the dissection is above the gonadal vessels, the ureter should also be posterior and out of harm’s way. Sometimes, the ureter is difficult to clearly identify and is most often confused with the gonadal vessels. Under these circumstances, it is important to remember several principles. The ureter runs longitudinally through the retroperitoneum. It never branches, as do blood vessels, and when manipulated, it should show evidence of peristalsis (Fig. 25-8). If the ureter cannot be identified secondary to inflammation or tumor, the ureter should be identified higher in the abdomen, where the anatomy may be more normal, and followed distally. If it is anticipated that ureteral identifica tion will be difficult, placing ureteral stents preoperatively can be quite helpful.

Figure 25-8 Retroperitoneum after dissection and removal of the rectum and associated lymphatics. Note the direction of the ureter, which is parallel to the aorta, compared with the gonadal vessels, which veer laterally. Also note that the ureter passes beneath the gonadal vessels.

Grade 2 complication

Splenic Injury

When the splenic flexure is mobilized, the spleen can be injured and cause troublesome bleeding.¹⁵ This complication is possible with any intra-abdominal colon operation and is reviewed in detail elsewhere. Most splenic injuries originate from omental attachments to the splenic capsule. With downward retraction on the colon, these attachments are torn off the splenic capsule, causing bleeding from the injured spleen. Fortunately, these attachments are unusual, but when identified, they need to be carefully divided (Fig. 25-9). If the splenic flexure is torn, troublesome bleeding will ensue. Most of the time, this bleeding is well controlled with simple packing, but on occasion, bleeding will persist. Although other maneuvers to control bleeding are available, the surgeon should not hesi-tate to perform a splenectomy if the bleeding is not well controlled.

Figure 25-9 Omental attachments to the spleen (A), which needs to be divided (B) to prevent injury to the spleen with downward retraction of the colon.

Grade 1/2 complication

Rectal Mobilization

An understanding of rectal anatomy is critical to proper rectal mobilization. The rectum is surrounded by a large amount of fat containing the mesentery and lymphatics to the rectum itself. This tissue is enveloped by a thin layer of fascia, known as the fascia propria. An avascular plane exists between the fascia propria and the presacral fascia, which is adherent to the periosteum of the sacrum. The retrorectal fascia, or Waldeyer’s fascia, is a thick layer of fascia connecting the presacral fascia to the fascia propria of the rectum. Division of this fascia is necessary to mobilize the distal rectum, and when divided, the rectum will lift from the sacral hollow and begin a more anterior approach. This greatly lengthens the rectum, especially posteriorly. For this reason, a low-lying posterior tumor may elevate significantly after division of the retrorectal fascia, allowing for a low anterior resection. Anteriorly, the rectum is more fixed and will not lengthen as much with mobilization. Therefore, a low-lying anterior tumor will more likely require an abdominal perineal resection than would a posterior-based tumor at the same preoperative level.

Rectal mobilization begins by entering the retrorectal space at the level of the sacral promontory (see Fig. 25-5). Division of the peritoneum at this level will identify the avascular plane between the mesorectum and the presacral fascia. The peritoneum lateral to the rectum is then incised toward the anterior cul-de-sac bilaterally. Finally, the anterior peritoneum also needs to be divided, which will allow entrance into the proper plane to mobilize the vagina in a woman, or the seminal vesicles and prostate in a man. Once the peritoneum is completely incised, the rectum is further mobilized by dividing the areolar tissue that exists between the fascia propria of the rectum and the fascia of the pelvic sidewall, collectively referred to as the endopelvic fascia. This dissection is greatly facilitated by proper deep pelvic retractors and anterior retraction of the rectum (Fig. 25-10). This dissection should be continued posteriorly and in the midline as deep as possible (Fig. 25-11). This will help identify the proper lateral plane, which should continue just adjacent to the mesorectum. Finally, the anterior plane needs to be developed, separating either the vagina or the prostate from the rectum (Figs. 25-12 and 25-13). This is greatly facilitated by using a lipped pelvic retractor and anterior traction on the vagina or prostate while using the hand for posterior traction of the rectum. Whereas this description implies that the posterior, lateral, and anterior dissections are done sequentially, in reality the surgeon needs to constantly adjust her or his retractors to dissect the area that is currently best exposed and continue this dissection circumferentially all the way to the pelvic floor. When this is done properly, there should be no mesorectum at the pelvic floor, thus completing a total mesorectal excision. Therefore, all that should be left is the rectum itself as it enters the rectal ampulla between the muscles of the pelvic floor. Division of the rectum at this level can almost always be done with one fire of a 30-mm transverse stapling device. Figure 25-14 shows the final appearance of the sacral hollow after complete removal of the rectum and the associated mesorectum.

Figure 25-10 Deep pelvic retractors.

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