Four main zones have been identified as being at high risk for nerve injury during total mesorectal excision [40–42]:

Moreover, damage to the pelvic nerves may occur during intersphincteric resection or abdominoperineal resection.

Ligation of the inferior mesenteric artery : ligation or stapling at the origin of the inferior mesenteric artery has the objective of complete removal of the regional lymph nodes. To avoid injury to the superior hypogastric plexus, it is important to identify the nervous fibers that run along the aorta and gently displace them before dividing the IMA (Fig. 14.3).

Sharp dissection is then continued down in order to identify the virtual space between the fascia propria of the mesorectum and the presacral parietal fascia. If the posterior plane of dissection of the mesorectum is correct, then it should be easy to identify the hypogastric nerves. If the dissection is carried below the parietal fascia an injury to the hypogastric nerves can occur. Conversely, if the dissection plane is too superficial the mesorectal fascia will be infracted. This can affect the quality of the specimen and is directly associated with the risk of local recurrence, as demonstrated by Quirke and Dixon [43].

The dissection then proceeds toward the anterior isolation of the rectum where this organ is in close contact with the nerves that originate from the inferior hypogastric plexus and carry both sympathetic and parasympathetic fibers to the bladder and sexual organs via the neurovascular bundles. They are located lateral to Denonvillier’s fascia in close proximity to the seminal vesicles. Every effort should be made to preserve both bundles when not involved by the tumor. If both nerves are sectioned, the rate of impotence will be 100 % [44]. However, potency rates will decrease substantially even when only one of the neurovascular bundles is left intact [45, 46].

In the case of involvement of the anterior wall of the rectum by the tumor, Denonvillier’s fascia should then be removed, as described by Heald, in order to reduce the risk of a positive circumferential margin. However, particular attention should be paid when dissecting the lateral margins of the rectoprostatic fascia and the rectovaginal septum that are in close relationship with the fibers of the inferior hypogastric plexus for the genitalia.

In most cases, when there is no anterior extrafascial extension of cancer and therefore no risk of neurovascular bundle involvement, it is possible to maintain the dissection plane closer to the mesorectal fascia and away from the seminal vesicles. When the tumor is located in the posterior rectal wall Denonviller’s fascia can be preserved [15, 47].

Different mechanisms of nerve lesions are considered to lie at the basis of genitourinary dysfunction in intersphincteric and abdominoperineal resection. A more extensive pelvic dissection, with an increased risk of pelvic nerve injury is common for both types of operation: different studies have shown a direct correlation between the distance of the tumor from the anal verge and the postoperative dysfunction rates [24, 48, 49]. There is nonetheless a general consensus that abdominoperineal resection has the worse functional outcomes [7, 18, 50–52]. The distortion of pelvic floor anatomy may not only lead to a loss of support for the urethra and the bladder but may also alter the mechanism of contraction of the bulbocavernous muscle which is involved in erection function and ejaculation [53, 54].

Various techniques and approaches have been developed for robotic total mesorectal excision [55–61]. However, most of the principles and points to be considered for the preservation of the autonomic nerves during surgical dissection are similar regardless of the technique applied.

Thermal, mechanical, and vascular damage are the principal causes of nerve injury and consequent urinary and sexual dysfunction. The extensive use of electrocoagulation should be avoided in particular on the lateral plane of dissection due to the anatomical proximity between the mesorectal fascia and the hypogastric plexus, and on the anterolateral plane, near the vesicles, where the neurovascular bundle is in close contact with the rectum. When needed, surgical clips should be applied for hemostasis. Excessive traction has been identified as a cause of neuropraxia that can lead to a temporary or unrecoverable blockage of nerve conduction depending on the grade and the duration of the traction [62, 63]. Delicate handling of the neurovascular tissue is also important to preserve the vasa nervorum and to prevent ischemic damage to the nerves. Traction-free techniques and gentle handling can be difficult during the learning curve phase in robotic surgery due to the absence of haptic feedback, when the surgeon has not yet learned to compensate this lack of sensation with visual integration. This issue is also important for the assistant surgeon whose main function is, for the most part, to provide countertraction during the intervention. Trainees should be instructed to avoid excessive tension during tissue manipulation [64].

The identification of all the components of the hypogastric plexus is of paramount importance to reduce the incidence of genitourinary dysfunction and injury can occur if the autonomic nerves cannot be kept under visual control during the dissection [65–68]. For this reason bleeding control is important because excessive blood in the operating field can make it very difficult to identify the nerves [13, 69]. The three-dimensional magnified High Definition view coupled with a stable camera platform offered by the da Vinci System helps in recognizing the smaller anatomical structures of the inferior hypogastric plexus and the anatomical planes, in particular during the anterior isolation of the mesorectum, which represents the most dangerous phase, where there is a high risk of lesion to the neurovascular bundle. The significant reduction of intraoperative blood loss reported may also contribute to the identification of the autonomic nerves [18, 70]. Moreover, the stability and superior movements with the increased flexibility and precision of robotic arms permit a more accurate dissection, especially in narrow spaces such as the conically shaped male pelvis and reduce the risk of collateral damage to surrounding tissues [56]. Quality of dissection and preservation of sexual and urinary function are, in fact, directly related [71] (Fig. 14.4). As a mnemonic for the trainee surgeons starting their surgical activity at the console we explain that robotic nerve sparing total mesorectal excision should be CLEAN: Circumferential from posterior to anterior as described by Heald; with Light tension on the structures; Electrocoagulation-free; Atraumatic to preserve the vasa nervorum and Nerve-guided: following the autonomic nerves (Table 14.1).

The primary objective of rectal cancer surgery is to obtain oncologic radicality to thereby minimize local recurrence. However, quality of life (QoL) is an important variable of oncological excellence and the ideal approach for the prevention of genitourinary complications of rectal cancer treatment is multidisciplinary with a close collaboration between the different specialists.

Since the inception of techniques aiming at the preservation of the autonomic nervous system during TME, the incidence of sexual and urinary dysfunctions has decreased.

The da Vinci surgical system is a powerful tool that offers more precision, more dexterity, and a better view of the operating field during total mesorectal excision. Nevertheless, we should bear in mind that the robot only enhances the skills and the capabilities of the surgeon. To achieve good results it is essential to have a sound knowledge of pelvic neuroanatomy and of the principles of nerve-sparing total mesorectal excision.