Autonomic nerve preserving in laparoscopic total mesorectal excision

Introduction

The adoption of total mesenteric excision (TME) and combined modality therapy has dramatically improved the oncologic outcome for the patients with rectal cancer during the last 3 decades (1,2). Nonetheless, the improved survival was constantly in company with high incidence of organ dysfunction which might severely compromise quality of life (3,4). In addition to the anterior rectal syndrome, urogenital dysfunctions due to intraoperative inadvertent pelvic autonomic nerve damage are well-recognized complications after rectal cancer surgery (5). The incidence of urinary dysfunction including difficulty emptying the bladder and urinary incontinence has been reported from 0% to 35% (4,6). Male sexual dysfunction includes erectile and ejaculatory problems may reach as high as 79.8% and 72.2%, respectively. For females, sexual dysfunction in relation to dyspareunia, difficulty to achieve orgasm and insufficient vaginal lubrication, is plagued but poorly defined and likely neglected in clinical practice (7,8).

Pelvic autonomic nerve preservation under direct visualization and sharp dissection may be limited and challenging by the anatomical constrains of the curved narrow pelvis, especially for the android pelvis with hypertrophic mesorectum. Laparoscopic technology with the advantages of direct illumination and magnification may enable better visualization and thereby hypothetically help to improve pelvic autonomic nerve preservation. As in previous studies, two multicenter randomized control trails comparing laparoscopic with open surgery have reported worse sexual function in laparoscopic surgery (4,9). While, the later studies showed no differences in outcomes or even in favor of laparoscopic to compare with open surgery (10,11). The increased experience with laparoscopic and understanding of the pelvic nerve anatomy may relate to the improving functional outcomes. A trend towards fewer incidences of urogenital dysfunctions is noticeable with the practice of pelvic autonomic nerve preservation adherence to the TME principles (5,10,12,13).

We believe that favorable urinary and sexual function could be achieved with enhanced vision, adequate traction and countertraction during the laparoscopic TME. Here, we discuss the current understanding of anatomy, key zones at risk and tips and tricks of nerve preservation during the laparoscopic TME (Figure 1).

Figure 1 Video of autonomic nerve preserving in laparoscopic total mesorectal excision (14). Available online: http://www.asvide.com/articles/1517

Pelvic autonomic nerve anatomy

Superior hypogastric plexus (SHP) and hypogastric nerves (HN)

The SHP is a network of pre- and post-ganglionic nerves overlying the abdominal aorta. The plexus is located anterior of the fifth lumbar vertebrae, starts underneath of the inferior mesenteric artery (IMA), run over the sacral promontory and then bifurcates into the right and left HN (15,16). The paired HN run about 2 cm medially to the ureter, move obliquely along the posterolateral wall of the pelvis and finally end as afferent fibres of inferior hypogastric plexus (IHP). The SHP comprises sympathetic nerves, which is originated from the sympathetic trunks alongside the tenth thoracic to the third lumbar vertebrae. Injury to the SHP or HN may result in troubles of ejaculation, decreased orgasm and urinary incontinence (16).

IHP and pelvic splanchnic nerves (PSN)

Besides the sympathetic fibres from the HN, the IHP also receives pelvic parasympathetic fibres from the PSN. The splanchnic nerves arising from the ventral roots of S2–S5 enter the pelvis through sacral foramina, running immediately ventral to the piriform muscles, together with the HN forming the IHP that lies laterally on the pelvic wall at the level of the lower third of rectum. Some branches of the splanchnic nerves run medially to the rectum via the so called “lateral ligaments” and make up the medial segment of the IHP. The lateral ligaments are thought to be condensation of fascia on the dorsolateral side of rectum and connect the rectum to the pelvic parietal fascia. Some suggest the ligaments do not exist and the small, inconstant and frequently unilateral middle rectal artery cross the mesorectum independent of any structure (16-18). The anterior portion of the IHP innervates the bladder and sexual organs. In women, fibers from the IHP travel through underneath the intersection of the ureter and uterine artery to the vesicovaginal and rectovaginal septum forming branches to the bladder, the vagina and the uterus (19). In men, these run in the neurovascular bundles (NVB) incline anteriorly at the lateral corners of the seminal vesicles in the 2 o’clock and 10 o’clock direction. These nerves run laterally outside the Denonvillier’s fascia and continue on the periprostatic plexus supplying branches to the prostate, seminal vesicles, cavernous bodies, and the vas deferens (16,20).

Key zones at risk

Origin of the IMA

The SHP is vulnerable to intercepted during high ligation of the IMA which is intended to achieve complete removal of regional lymph nodes. The SHP fibres lie in front of the aorta and are located in a wide area of dissection. The preaortic plexus injured if the IMA pedicle is ligated flush with the aorta (20). The left trunk of the SHP travels along the left side of the aorta and is very close to the IMA at its origin. So mass clamping of the IMA may increase the risk of damage to the left trunk of the plexus.

Posterior rectum

Although there is still controversy about the facial structures (21), posterior dissection of the rectum should carried out at the avascular plane of loose areolar tissue between the fascia propria anteriorly and the parietal fascia containing the HN posteriorly. A further loose areolar tissue layer could be easily created posterior to the HN. If dissection is too posterior and the HN appears to run into the mesorectum, both the HN and the presacral vein are at risk of damaging. The major risk is to enter the wrong plane at the transition of the mesosigmoid to the mesorectum or not following the correct plane during dissection.

Lateral rectum

At the high level lateral dissection of the mesorectum, the HN is vulnerable to injury if dissection starts or opens the laterorectal reflection of the peritoneum too laterally. During the low lateral dissection, the IHP is vulnerable to injury. The so called “lateral ligament” is a dense connective tissue between rectum and pelvic parietal fascia. The IHP is rarely seen in patients with high body mass index and bulky and fat mesorectum. Injury can occur if the lateral ligament bleeding is not control and blunt dissection is used or excessive medical traction and non-anatomical dissection.

Anterior rectum

There is a very narrow space between the mesorectum and the seminal vesicles and prostate or vaginal. The Denonvillier’s fascia is displaced anterior to the mesorectum and posterior to the seminal vesicles and prostate or vaginal. The NVB lie laterally anterior to the Denonvillier’s fascia and then go down to the urethra at the apex of the prostate. Excessive traction on the rectum “moves” the NVB in the dissection field on the lateral edges. Blind mass clamping if bleeding is not controlled contributes the damage of the NVB. There is no consensus concerning the proper anterior anatomical plane but if the tumor is anterior, the dissection should carry out anterior to the Denonvillier’s fascia, which presents a high risk of nerve damage.

Tips and tricks of nerve preservation in laparoscopic total mesorectal excision

In laparoscopic total mesorectal excision there are a few key zones at risk of nerve injury as mentioned above. To ensure the preservation of pelvic autonomic nerve, a proper surgical technique with step-by-step checklist at the critical points should be carried on without compromise of oncological outcome.

Laparoscopic TME usually starts with a peritoneal incision at the surface of the sacral promontory, dissection from medial to lateral and extend up underneath the duodenum, and then meet the first key area for injury of the IHP. The key of nerve preservation is finding the plane by maintaining sufficient tension. With the help of the assistant lifting the pedicle of the IMA, dissection of the posterior of the IMA could be easy. Under the magnified laparoscopic view, the SHP is visualized covered with ventral fascia. By opening the artery sheath and ligating the pedicle at a distance of 1.5–2 cm from the aorta, the SHP fibres lying in front of the aorta are preserved. Avoiding mass clamping of the IMA and preserving the Gerona’s fascia is needed for the left trunk of the SHP running along the left side of the aorta (Figure 2).

Figure 2 The SHP is a network of pre- and post-ganglionic nerves overlying the abdominal aorta. By opening the IMA sheath and ligating the pedicle at a distance of 1.5–2 cm from the aorta, Avoiding mass clamping of the IMA, the SHP fibres lying in front of the aorta are preserved. SHP, superior hypogastric plexus; IMA, inferior mesenteric artery.

After the dissection of the left Toldt’s space and complete the mobilization of the sigmoid and descend colon, the transition from mesosigmoid to mesorectum is the second zone of iatrogenic nerve injury for the HN. Kinugasa suggest the pre- hypogastric nerves (pre-HGN) fascia anterior to the HN is evident based on historical examination in the retrorectal multilaminar structure. Posterior dissection should be performed at the loose areolar layer between the rectal proper fascia and the pre-HGN fascia (Figure 3). The superior rectal artery is situated just anterior to the rectal propria fascia, which could be used as a landmark to find the plane. Surgeons should follow the plane but not create a new plane, use left hand to counter-traction to keep sufficient tension and keep fascia of rectum clear from other tissue (Figure 4).

Figure 3 The pre-HGN fascia is anterior to the HN. Dissection should be performed at the loose areolar layer between the rectal proper fascia and the pre-HGN fascia along the dotted line. HGN, hypogastric nerve.

Figure 4 Dissection is too posterior and the pre-HGN fascia is opened. Both the HN and the presacral vein are at risk of damaging. Pentagram shows the wrong plane. HGN, hypogastric nerve.

Going all the way down to the level of the forth sacral vertebral will meet the so-called rectosacral fascia which was thought to be a surgical artifact in Kinugasa’s study (21). A sharp incision though this plane will be another loose areolar layer without any risk of nerve damage. The lateral dissection is the third risk zone for injury of the HN and IHP. The lateral dissection is done after the posterior midline dissection has gone as far down to the anorectal junction as possible. Lateral dissection moves from the posterior midline to the left and right posterolateral pelvic wall (Figure 5). Some authors suggest under the illumination and magnification of the laparoscopic technology, the autonomic nerves can serve as the landmark and develop a novel concept of nerve-oriented mesorectal excision. However, The IHP is covered by parietal fascia and rarely seen in obese patients (22). Dissection along the fascia propria may be more appropriate (Figure 6). Identification of the site where fascia of rectum and IHP merge together is needed. Typically, there is a triangle space lying below rectal fascia and nerve plexus. Extending laterally along the line through the triangular space, the IHP attaching to rectal fascia is effectively shrunk. Dissection need be cautious not to break into the mesorectum or the nerve plexus and always keep good tension and small bite. Using the tips mentioned above, the adherent nerves can be slightly teased and peeled off the rectal fascia. After open the laterorectal reflection of the pararectal peritoneum, dissection to the supra-levator space and anterior plane is one of the most vulnerable parts of mesorectum and nerve plexus. Mesorectum stretching out laterally like a coconut rather than cylinder (Figure 7). In order to avoid leftover of mesorectum, dissection should always follow the arc of pelvic floor from posterior to lateral and from known to unknown. After fully mobilization, a clear coconut-like structure can be seen and mesorectum is completely removed.

Figure 5 The inferior hypogastric plexus receives fibres from the pelvic splanchnic nerves. There is always a Triangle space lying below rectal fascia and nerve plexus and extending laterally along the line through the triangular space.

Figure 6 Dissection along the fascia propria and extending laterally along the line through the triangular space is more appropriate.

Figure 7 Coronal CT image demonstrates the mesorectum stretching out laterally like a coconut rather than cylinder. Dissection should always follow the arc of pelvic floor from posterior to lateral.

After complete mobilization of the supra-levator space and lateral part of mesorectum, peritoneum is incised about 0.5 cm anterior to the peritoneal reflection. Here we enter the space anterior to Denonvillier’s fascia and meet a new risk area of autonomic never injury. Although Heald suggest the Denonvillier’s fascia forms the anterior surface of the mesorectum, most opinions recommend dissecting in front of Denonvillier’s fascia only when the tumor located anteriorly or there is a risk of compromised circumferential margin. For posterior and lateral tumors, our experience is to transect the Denonvillier’s fascia at the base of seminal vesicle, then dissection is along the propria fascia. Fully mobilization of posterior and lateral mesorectum greatly facilitates the preservation of NVB. Dissection just follows the groove and uses the hook parallel but not vertically to the rectal fascia. In some cases, it looks like there is a shining envelope containing the NVB when it is well preserved (Figure 8).

Figure 8 The NVB lie laterally anterior to the Denonvilliers fascia. Transect the Denonvilliers fascia at the base of seminal vesicle, then dissection is along the propria fascia. Fully mobilization of posterior and lateral mesorectum greatly facilitates the preservation of NVB. NVB, neurovascular bundle.

The adoption of TME and combined modality therapy has improved the oncologic outcome greatly in the patients with rectal cancer. Urogenital dysfunctions due to intraoperative inadvertent pelvic autonomic nerve damage are well-recognized. Surgeons should be familiar with the pelvic autonomic nerve anatomy especially the key zones at risk and take advantage of laparoscopic technique in order to improve the functional outcomes of TME.

Acknowledgments

Funding: None.

Footnote

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/jxym.2017.04.03). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Written informed consent was obtained from the patient for publication of this manuscript and any accompanying images.

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