Robotic Transanal Surgery for Rectal Cancer

Abstract

Robotic transanal surgery is the culmination of major developments in rectal cancer management and minimally invasive surgery. It is the result of continuous efforts to tackle the challenges inherent to rectal cancer surgery. This latest technology holds great promise and excitement for the care of the rectal cancer patient. In this article, we will describe the evolution of transanal rectal cancer surgery and describe how the convergence of transanal transabdominal, transanal endoscopic microsurgery, transanal minimally invasive surgery (TAMIS), transanal total mesorectal excision (taTME), and the different robotic platforms have culminated in the development of single port robotic transanal minimally invasive surgery (SP rTAMIS) and single port robotic transanal total mesorectal excision (SP rtaTME). We will describe the indications, technical aspects, outcomes, benefits, and limitations of the SP rTAMIS and SP rtaTME.

The challenges inherent to rectal cancer surgery have inspired numerous innovations in the field. Driven by high recurrence rates and high morbidity seen with the earliest operations, and by the technical difficulties of operating in the deep and narrow confines of the pelvis, the surgical treatment of rectal cancer has continued to evolve. Operating from above, the challenge is to obtain an adequate distal margin and perform an anastomosis to avoid permanent colostomy. Approaching the cancer transanally from below, the challenge is obtaining adequate cephalad reach to avoid positive proximal margins and piece-meal excisions. In both approaches, visualization, retraction, light, instrument reach, and precision are problematic. In response to these issues a multitude of strategies have been developed. Laparoscopic total mesorectal excision (TME), robotic TME, the transanal transabdominal (TATA), transanal total mesorectal excision (taTME), transanal endoscopic microsurgery (TEM), and transanal minimally invasive surgery (TAMIS) have all been employed to attempt to simplify matters for surgeons.

The singular truth remains that rectal cancer surgery is hard. In an effort to address the aforementioned issues of visualization, retraction, light, instrument reach, and precision in rectal surgery, some have opined that the robot is ideally suited. The 3D image, 360-degree wristed articulation of the instruments, and three-arm plus camera control by the robotic operator offer answers to many of these problems. In this chapter, we will be presenting the current state of, as well as our thoughts and approaches to, transanal robotic surgery for rectal cancer.

Basic Terminology

Transanal surgery, and therefore robotic transanal surgery, for rectal cancer comprises of two categories: local excision and radical surgery. The benefit of local excision is that it avoids the morbidity and mortality of major deep pelvic surgery. Of course, this comes at the cost of foregoing a formal cancer operation with proper lymphadenectomy. As a result, transanal local excision for rectal cancer is reserved for select early patients with properly downstaged cancers following neoadjuvant therapy in which sphincter and organ preservation are the goals. Transanal radical surgery has been performed as part of taTME, an approach developed from the TATA procedure, in an effort to facilitate the most difficult aspect of TME surgery. We will present these surgical approaches separately.

Robotic Transanal Surgery: Local Excision

Indications

In general, transanal excision is indicated for the local treatment of premalignant lesions or early cancers, where the goal is tumor eradication, without the need for lymph node sampling or fear of leaving residual invasive malignancy. Polyps containing a focus of neoplastic cells confined to the mucosa (pTis), also defined as high-grade dysplasia are associated with ≤2% risk of lymph node metastasis, and therefore complete local excision with polypectomy or endoscopic mucosal resection is usually curative. ^{1 2} For T1 tumors, defined as invasive adenocarcinoma invading into, but not beyond the submucosa, transanal excision remains an option. These are typically found in a pedunculated or sessile adenoma or nonulcerated lesion. When considering treatment options, the depth of T1 invasion into the submucosa should be further characterized using the Kikuchi classification, where Sm1 represents invasion into the upper third, Sm2 into the middle third, and Sm3 into the deepest third. ³ This is important to note, as multiple studies have shown that the extent of submucosal invasion is highly associated with the likelihood of lymph node positivity, with Sm1 lesions having a 0 to 3% lymph nodes positivity, behaving like Tis polyps, while T1 Sm 2 to 3 cancers, similar to T2 cancers, have a 15 to 25% lymph node positivity. ⁴ Therefore, local excision of T1 Sm1 lesions with negative margins is considered curative. The 2012 NCCN guidelines recommend local excision as an alternative approach for the management of select well to moderately-well differentiated, T1 rectal cancers within 8 cm of the anal verge without radiographic evidence of lymph node involvement, less than 3 cm in diameter and involving less than one-third of the rectum. ⁵

Given the unacceptably high local recurrence rates for high risk rectal cancers treated with local excision, we and several others have reported on the use of neoadjuvant chemoradiation therapy (CRT) prior to local excision of high-risk lesions. ⁶ When using neoadjuvant CRT in combination with local excision of T2 tumors, Lezoche et al reported similar local recurrence rates (6 vs. 8%) with local excision compared with radical resection, with a median follow-up of 9.6 years. ⁷ While detailed discussion of the use of TEM in high-risk rectal cancer is outside the scope of this chapter, it is worth noting that TEM is a viable option in select patients and should be considered a part of our surgical armamentarium.

Evolution of Transanal Surgery for Rectal Cancer

Video 1 Wristed and elbowed articulations of SP robot. SP, single port.

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Traditional transanal excision (TAE) using conventional instruments under direct visualization has been a mainstay of treatment for low rectal tumors for many years. This technique is often limited by poor visualization and difficulty reaching the cephalad margin of the lesion, limiting its utility to tumors in the lower third of the rectum. Additionally, TAE is often complicated by specimen fragmentation, which results in positive resection margins, a decreased quality of oncologic resection, and increased recurrence rates. ⁸

TEM, introduced in the early 1980s ushered a new era in the management of rectal neoplasms. ⁹ Conceived and developed by German surgeon Gerhard Buess, TEM was well ahead of its time. This technique provided benefits akin to laparoscopy, which would not be introduced for several more years, including improved visualization and reach. TEM is based on a stable platform using a Martin arm, which is intended to provide strong visual-spatial orientation, improved reach to the upper rectum, allowing surgeons to dissect larger and more proximal lesions when compared with TAE. ^{10 11} This disruptive surgical approach set the stage for the rapid evolution of technology in our specialty over the ensuing decades. While TEM is highly effective, the steep learning curve, technical limitations, and singular application of the equipment for local excision have limited its widespread use. The main technical challenge of TEM lies in operating solid shafted instruments through a rigid tube and the inability to move the instruments in a right or left fashion. This technique also requires constant repositioning of the TEM scope using the Martin arm to keep the target anatomy within reach; the fixed position of the lens in the top half of the TEM obturator limits instrument reach to the bottom 180 degrees of the TEM scope. This significant drawback is that it often requires complex set up or repositioning of the patient to obtain adequate exposure to work.

For low rectal cancers not appropriate for TEM that would have otherwise required a permanent colostomy, the transanal abdominal transanal (TATA) proctosigmoidectomy with descending coloanal anastomosis was developed. The TATA was first described in 1984 by Dr. Gerald Marks for low rectal cancer. The TATA was the first resectional procedure that ensured a known distal margin in the preirradiated rectum, expanding sphincter preservation surgery. Having a known distal margin facilitates a precise distal dissection, which is especially important after the downstaging of chemoradiation. It also eliminates the challenge for the surgeon of applying the stapler from above in cases with impalpable scar after chemoradiation. For cancers in the distal 3 cm that are mobile after radiation, the TATA technique allows sphincter preservation.

Perhaps not unexpectedly, surgeons began experimenting with advanced laparoscopic techniques introduced per anus. In that spirit, Albert et al introduced single incision laparoscopic surgery (SILS) transanally, becoming known as TAMIS. ¹² This technique uses a flexible SILS port inserted transanally rather than the rigid proctoscope used in TEM. Procedure costs are decreased by avoiding the large capital investment for TEM equipment and using laparoscopic instruments which are readily available in the operating room. While numerous studies have established the benefits of transanal minimally invasive approaches, it has become clear over time that TAMIS has its own challenges and a unique learning curve. ^{13 14} From an ergonomics standpoint, TAMIS remains rather limited, as the surgeon and the assistant must both fit between the patient's legs. Similar to TEM, straight shafted instruments are still problematic within the confined area of the rectal lumen, resulting in instrument collisions and poor target visualization during excision. While TAMIS offers great advantages to TEM, the combination of an unstable platform, poor ergonomics, and difficult positioning of the assistant, while not prohibitive, leave more to be desired.

Naturally, as experience with robotic surgery progressed, multiarm robotic platforms began to be used transanally. Atallah et al reported on the feasibility of robotic TAMIS using the da Vinci Si robotic platform in a cadaveric model in 2011. ¹⁵ This was followed by their report on the first human case with resection of an early-stage rectal cancer in 2012. ¹⁶ Since that time, several authors have reported on the feasibility and safety of robotic TAMIS. Some of the advantages of robotic surgery are its magnified high-definition 3D view, wristed movements with 6 degrees of freedom, tremor elimination, and improved ergonomics; allowing for greater surgical precision when compared with TEM and TAMIS platforms. ¹⁷ While it was initially used for local excision of rectal neoplasms, robotic TAMIS was soon adopted for more complex procedures, with the first report of robotic transanal surgery with total mesorectal excision (RTAS-TME) in 2013 by Atallah et al. ¹⁸

The first robotic system used for transanal local excision, the da Vinci Si robotic system, was limited by its four bulky arms and more restricted field of view, preventing effective treatment of more proximal rectal lesions. In an attempt to mitigate some of these limitations, Hompes et al used a transanal glove-port for local excision of malignant and benign rectal lesions in a series of 16 patients, which allowed for wider movement of instruments within the rectum and decreased external arm collision. ¹⁹ The next generation da Vinci Xi system partially addressed these system limitations with decreased arm bulk, allowing easier, quicker transanal docking and more proximal reach. However, the larger 8 mm instruments still present a significant issue in the small working space of the anus and rectum and significant arm clashing.

Despite the limitations of these multiarm robotic platforms, the limits of transanal robotics continued to be pushed. Atallah et al successfully performed taTME and repair of complex fistulae via robotic TAMIS. ²⁰ They reported on four patients who underwent RTAS-TME for invasive adenocarcinoma of the distal rectum. Their early experience noted that all specimens were found to be complete or near complete mesorectal excisions with negative distal and circumferential margins. ²⁰ Similarly, Gómez et al conducted a prospective pilot study (using the da Vinci Si) , where RTAS-TME was performed in five patients. In their report, all TME specimens showed complete mesorectal excision with negative distal and circumferential margins. ²¹

Transanal surgery is highly demanding due to the confined anatomical space in the pelvis, restricted exposure, and limited proximal reach. Conventional multitrocar robotic platforms were originally designed for transabdominal access. The effector arms of these systems are not flexible, limiting dexterity in the narrow pelvis. Furthermore, the 8-mm instruments add bulk and subtract from field view in this confined space, while the sacral angulation in the pelvis and instrument torque prevents dissection beyond 7 to 8 cm from the anal verge. Most importantly, while workable, transanal use of the Si and Xi da Vinci platforms represents a potential risk to the external sphincter complex. Taken together, these factors have proven to be major obstacles in the wide adoption of robotic transanal surgery.

With all these advances and limitations in mind, the da Vinci single port (SP) was introduced in 2018. The SP robot was developed for access to narrow anatomical areas that were difficult to reach; the prostate, throat, and rectum. The SP robot provides the advantages of robotic articulation and 3D visualization while avoiding the drawbacks of external arm collision; It is specifically designed for SP and endoluminal surgery. The 25-mm SP robotic trocar allows for insertion of the robotic camera and three instruments within a confined space ( Fig. 1 ). Our early experience with SP robotic transanal local excision, which we refer to as SP rTAMIS, found that docking of the SP robot was mastered quickly and with significant reproducibility. There is a minimal time required for set-up and this compares favorably to our TEM set-up experiences and is slightly longer than set-up for traditional TAMIS cases. This ease of docking the SP robot addresses complaints surrounding extended set-up times with multiarm robotic systems in the past. ²²

Fig. 1.

SP robotic trocar with camera and three instruments. SP, single port.

The SP robot consists of a “C-arm” which provides 360-degree rotation both around the remote center of the cannula and within the instrument port, which we have found to be immensely useful for transanal robotic surgery. This rotation allows visualization of all quadrants of the rectum without the need for repositioning or redocking of the robot. The wristed and elbowed articulations of the instruments allow for triangulation around the target anatomy and improve the ease of dissection ( Video 1 ). Additionally, the SP articulation helps to minimize collisions between instruments and facilitates intraluminal suturing and tying. From an ergonomics standpoint, there is no competition for workspace between the surgeon and the assistant.

SP rTAMIS: Description of the Technique

Video 2 Assistant port used for passing suture/suction.

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Video 3 SP robotic suturing. SP, single port.

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The operation is started with the patient in modified lithotomy; the legs are positioned so as to have the anus over the edge of the operative table by approximately 4 cm. A GelPoint Path transanal access channel (Applied Medical Inc, Rancho Santa Margarita, CA) is inserted transanally and secured to the patient's skin with sutures. The GelSeal cap is then secured to the access channel containing the SP robotic trocar and an AirSeal assistant trocar located on the patient's right. The SP robot is then brought in between the patient's legs and docked to the SP multiport trocar. The SP camera is inserted, followed by Cadiere forceps in port 1, fenestrated bipolar in port 2, and hook cautery in port 3. The instruments are advanced and the lesion is identified. The assistant port is used for suction and passing suture as needed ( Video 2 ).

After the lesion is identified, the mucosa is scored circumferentially around the lesion with cautery marking a 1 cm margin. The dissection of the lesion is performed to the appropriate depth, depending on the pathology, in the same way as is done for TAMIS/TEM. Prior to complete excision, we find it useful to orient the specimen by placing a single suture at the inferior aspect of the lesion ( Fig. 2 ). After the lesion is excised, it is brought into the port, out of the operative field. The specimen is not immediately removed to avoid undocking and re-docking of the robot.

Fig. 2.

Orienting the specimen.

Next, we clean all of the instruments, irrigate the operative field with betadine, and change gloves to minimize the likelihood of tumor implantation into the wound. After irrigation, Cadiere forceps are loaded into port one, and needle drivers are loaded onto ports 2 and 3. A 3–0 Vicryl suture cut to 15 cm is introduced via the assistant port. The defect is closed with full thickness bites and can be closed in a running or interrupted fashion with robotic tying ( Video 3 ). It is often helpful to start the closure in the middle of the defect to minimize tension on the defect as you are closing. A major benefit of the third arm is the ability to follow your suture as one is closing to keep the tension appropriate, in the same way as is done in open surgery ( Fig. 3 ). After careful inspection of the repair, the SP robotic instruments and the GelPOINT path are removed.

Fig. 3.

Using SP third arm for retraction. SP, single port.

Outcomes

In our early experience with SP rTAMIS, we have noted good clinical outcomes. The reach and excellent visualization afforded by the SP robot have resulted in no fragmented specimens and no positive margins. While we cannot share our full data for the SP rTAMIS, as it is pending publication, our outcomes are similar to our previously published experience with TEM. ¹⁴ Our results are also similar to ports of TEM/TAMIS experiences, improved from TAE results for local recurrence referenced earlier. These benefits are generally attributed to difficulties in reaching cephalad tumor margins by standard transanal approaches. In our early unpublished experience, we have noted complication rates similar to TEM and TAMIS experiences, with no wound separations in nonirradiated wounds and a 22% minor separation rate following chemoradiation. We have noted no mortalities.

Robotic Transanal Surgery: taTME

Evolution of taTME: from TATA to SP r-taTME

The taTME era has its origin with the development of TATA proctectomy described in 1984 by Dr. Gerald Marks for low rectal cancer. ²³ The TATA ensures a known distal margin in the preirradiated rectum and expands sphincter preservation surgery. Inadvertently, it also addressed the most difficult aspect of the pelvic dissection first, facilitating the abdominal operation later, which is the essence of the taTME. With the advent of laparoscopy, Dr. John Marks and Dr, Kim started in 1998 doing the abdominal portion of the operation laparoscopically. ²⁴ This technique that we have described extensively, ²⁵ has proved to have excellent oncological and functional outcomes. ^{26 27}

As noted previously in 2009, Drs. Atallah, Albert and Larach described TAMIS, a cost-effective alternative to TEM. In December of 2008 and then in 2009 Drs. Marks and Sylla, separately, applied the TEM platform to perform the first taTME ushering in the modern era of taTME.

Pushing the limits of transanal surgery using the TAMIS platform, Dr. Leroy pioneered “pure” NOTES proctosigmoidectomy with transanal completion of the TME dissection, release of the splenic flexure, transection of the inferior mesenteric vessels and coloanal anastomosis. He coined the procedure perirectal oncologic gateway for retroperitoneal endoscopic single site surgery (PROGRESS). ²⁸ Select centers have further pioneered pure NOTES taTME. ^{29 30}

However, taTME is a technically challenging procedure with a steep learning curve, which represents a major obstacle to wider adoption.

Robotic transanal surgery has been proposed by some as a way to overcome some of the technical challenges of reach, visualization, retraction, and ergonomics. Its articulated instruments, improved ergonomics, and high-definition three-dimensional view are considered optimal for the precise dissection, identification, and preservation of the nerves, especially when operating transanally. After demonstrating the feasibility of robotic TAMIS for local excision using the daVinci Si robotic platform in 2012, ¹⁶ Atallah et al reported the first robotic transanal TME a year later. ¹⁸ The SP rtaTME represents the natural evolution of this process.

Indications for taTME

While a great deal of overlap exists regarding approaches, in general we approach upper rectal cancers laparoscopically from above, mid rectal cancers by the Xi robot transabdominally, and taTME surgery is employed for cancer in the distal third of the rectum. Some surgeons utilize taTME for mid and upper rectal cancers, so if that is one's preferred approach, the robot can be used and the discussion that follows would apply to more proximally based cancers. In our unit, the taTME and TATA approach are for nonfixed cancers after chemoradiation, that would typically be treated by an abdominoperineal resection. taTME/TATA is utilized after neoadjuvant therapy has downstaged the tumor extending the possibility for sphincter preservation. Only those patients who are incontinent to begin with or whose cancer remains fixed 12 weeks after completion of their chemoradiotherapy undergo abdominoperineal resection, at a rate of 7% in our unit. The other patients are treated using the TATA/taTME technique. As stated, this allows for a known distal margin from the tumor. By extending this dissection transanally with the use of a port and laparoscopic and now robotic instrumentation from below, the TME dissection is routinely performed into the abdominal cavity.

Techniques for TATA/taTME

There are multiple ways to perform a taTME. A majority of surgeons prefer to start the TME dissection from above, taking it as low as possible and only going below to finish the dissection and do the anastomosis. We always start the operation transanally to address the most difficult part of the operation first and take the dissection as proximally as possible. We do this first portion in an open fashion to the level of the seminal vesicles or cervix. Once this is done, the taTME can be carried either laparoscopically or robotically using the Xi or SP robots. We take the dissection as cephalad as technically possible. The transabdominal portion can then be performed either laparoscopically, multiport, or most often with a SP at the ileostomy site, or robotically using the Xi or SP robot. In select cases, we can perform the entire procedure transanally, including taking the inferior mesenteric vessels, releasing the splenic flexure, and performing the anastomosis. ³⁰

SP rTATA/taTME: Description of the Technique

Video 4 Docking the SP robot transanally. SP, single port.

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Video 5 Inserting and advancing SP instruments. SP, single port.

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Video 6 Obtaining hemostasis with SP bipolar forceps. SP, single port.

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Video 7 Transanal ligation of the IMA. IMA, inferior mesenteric artery.

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The operation is started with the patient in the extended lithotomy position in Skytron leg holders. The legs are positioned so as to have the anus hang 4 cm off the operative table. The open transanal portion of the case begins with infiltrating the perianal skin and levator musculature with xylocaine-epinephrine solution to minimize bleeding. Four Allis-Adair clamps are applied at the 12, 3, 6, and 9 o'clock position. A key aspect of the operation is to incise the mucosa circumferentially at the level of dentate line using electrocautery, to avoid radial tearing of the distal margin later in the dissection. The Metzenbaum scissors are then used to spread just off the posterior midline to enter through the full thickness of the rectal wall (which at this level is the upper aspect of the internal sphincter) ( Fig. 4 ) and into the intersphincteric plane. The key anatomical area to see at this point is the glistening white endopelvic fascia of the puborectalis. This allows the surgeon to be certain that he has entered into the proper plane of dissection between the levator ani complex and the embryologic package of the mesorectum. This is the most critical aspect of the operation from an oncologic and functional standpoint; if one is too superficial, the mesorectum is injured and the cancer violated, if too deep the puborectalis is injured resulting in impaired function. The dissection is taken circumferentially perpendicular to the axis of the anal canal. Great care must be taken not to go too anterior into the intraprostatic urethra or anterior to the prostate higher up. The dissection is taken up as high as possible, generally to the level of the cervix in women and the level of the seminal vesicles in men. Once this is completed, a 0-Vicryl suture is used to close the rectum circumferentially in an airtight fashion. A fuller description of this aspect of the procedure and our outcomes have been described elsewhere. ³¹

Fig. 4.

Dissecting into the intersphincteric plane.

Other surgeons performing Xi/Si robotic taTME, begin the operation by first placing a watertight intraluminal purse string followed by insertion of the gelPOINT path. ²⁰ This is critical to avoid both tumor spillage into the operative field as well as distention of the proximal bowel which will interfere with the abdominal portion of the procedure. They then perform the initial dissection with the robot before entering into the extramesorectal plane. This approach offers excellent visualization but loses the palpable direction anteriorly which can result in straying into the urethra and prostate.

For the SP rtaTME, a GelPoint Path transanal access channel (Applied Medical Inc, Rancho Santa Margarita, CA) is inserted transanally and secured to the patient's skin with sutures once the rectum has been oversewn ( Fig. 5 ). The GelSeal cap is then secured to the access channel containing the SP robotic trocar and an AirSeal assistant trocar located on the patient's left. The SP robot is then brought in between the patient's legs and docked to the SP multiport trocar ( Video 4 ). The SP camera is inserted first followed by a Cadiere forceps, fenestrated bipolar forceps, and scissors in ports 1, 2, and 3 respectively ( Video 5 ). The dissection is carried in a circumferential fashion using scissors. By performing the dissection in a circumferential fashion, the areolar tissue plane is entered and directs the dissection in the proper plane. The dissection is performed sharply as the proper embryologic plane should be relatively bloodless. Monopolar cautery is used with the scissors to address small bleeders. If more significant bleeding is encountered, the surgeon should reevaluate his plane of dissection, but also use the bipolar graspers in arm 2 to gain hemostasis ( Video 6 ). An additional benefit of sharp dissection is that a small amount of smoke, even with active smoke evacuation, severely limits the view in the small area of the pelvis. Constant reorientation needs to be maintained during the dissection to avoid straying laterally into the obturator fossa on the right and the left side. In the posterior midline, the surgeon must remind himself that the presacral hollow curves superiorly, and if the dissection is taken straight back, the presacral veins will be injured. The anterior dissection is performed, the pouch of Douglas is incised, and the peritoneum is entered.

Fig. 5.

GelPoint transanal access channel.

At this point, one can proceed with the abdominal portion either transabdominally, using the SP or Xi robot or standard multiport or SP laparoscopic technique. As stated earlier, some surgeons prefer to start the operation abdominally or work simultaneously from above or below. It is our opinion that the major benefit of taTME, laparoscopically or robotically, is to address the most difficult portion of the operation first transanally, which is lost if the operation commences from above. The ability to operate as two teams simultaneously is greatly impaired by the footprint of the robot over the abdomen when performing SP rtaTME, effectively eliminating the two team approach as an option.

On select occasions, as we have described doing via laparoscopic taTME, ³⁰ we continue the entire abdominal dissection transanally.

For the purpose of this study we will describe the technique of a pure NOTES procedure with SP rtaTME, with transanal splenic flexure release, vascular control, and colonic mobilization. Once the anterior peritoneal reflection is transected, the rectum is gently pushed cephalad into the peritoneal cavity. This results in tenting of the sigmoid mesentery and lateral peritoneal attachments. The retroperitoneal dissection of the mesorectum and retroperitoneum is continued to reveal the origin of the inferior mesenteric artery (IMA). The left ureter must be identified, and care should be taken as it is encountered quite quickly at the pelvic brim during the early stages of the transanally initiated abdominal dissection. Since the SP robot lacks a stapler device, a high ligation of the IMA is performed using clips. It is then divided with either scissors or a LigaSure introduced via the assistant port ( Video 7 ). The inferior mesenteric vein is then transected centrally.

Mobilization of the sigmoid colon posteriorly off of the retroperitoneum and Gerota's fascia, and laterally at Toldt's fascia is performed and the splenic flexure is always mobilized for a tension-free anastomosis. Once this is done, the robot is undocked and the specimen is delivered transanally.

The anastomosis may be a side-to-end, J pouch or end-to-end coloanal anastomosis. We usually prefer to perform a well vascularized handsewn end-to-end anastomosis without tension, as opposed to straining, to create a side-to-end anastomosis or colonic J pouch and putting the mesentery on stretch. All patients with coloanal anastomosis are diverted proximally.

Outcomes

We published our long-term outcome of patients who underwent TATA/taTME and showed low local recurrence rates and excellent overall survival. ²⁶ We also showed that satisfaction with quality of life and functional outcomes is high after TATA. ²⁷ Patients clearly preferred this approach over having a permanent stoma. Data regarding the use of robotic taTME is scarce. We are currently investigating the outcomes of SP taTME in a prospective trial.

Benefits and Limitations

Video 8 Articulation of SP instruments transanally. SP, single port.

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This report is based on our experience with SP rTAMIS for transanal excision of rectal lesions and SP rtaTME. Certainly, a fuller understanding of the capabilities of the SP robot for transanal surgery, as well as the limitations and drawbacks, will become clearer as greater experience is gained at other institutions and with other surgeons worldwide.

It is important to note that the SP platform is not currently FDA approved for colorectal surgery and is only for urology and ENT surgery. That being said, experience with SP rTAMIS worldwide is minimal, and our treatment was provided as part of an IRB approved trial registered with clinicaltrials.gov (NCT03700593). However, it is clear that the SP robotic platform addresses many of the previous limitations of TEM and TAMIS. TEM is limited by the need for a dedicated unit/equipment just for transanal surgery, making its availability limited to select specialty centers. Additionally, the lesion is required to be in the bottom 180 degrees of the field to facilitate reach, the mobility of the platform is quite cumbersome requiring numerous adjustments and repositioning during the case, and the long shaft of the operating tube makes suturing and tying cumbersome if not impossible. While TAMIS has addressed many of the above issues, challenges exist regarding the lack of a stable platform, ergonomically challenging positioning of the surgeon and assistant between the legs, and difficulty in tying in the lumen. With enhanced 3D visualization, double-wristed operating arms, and compact access via a single 25-mm channel, the SP robot addresses most of these issues. SP rTAMIS provides a significant technical enhancement of the environment for transanal endoluminal surgery allowing the surgeon as well as the bedside assistant to operate comfortably in a seated position. Set up for the procedure and dock is quick and easy with foot-controlled manipulation from the console.

For SP rtaTME, a major advantage of the SP robot in comparison to laparoscopy is the use of three arms/instruments as compared with only two laparoscopically. This allows the surgeon to create a similar environment to open surgery where one instrument is used for retraction, and two hands are used to dissect. This ability to create traction and counter-traction in the plane of dissection is invaluable to stay in the proper plane. Furthermore, the elbow and wristed articulation of the SP robotic instruments allows triangulation, preventing clash in the narrow transanal space ( Video 8 ). Lastly, the ability to adjust the entire operative field by moving the robotic cannula and all four arms simultaneously at the fulcrum of the anus entirely eliminates the clashing of arms encountered with other robots. A holograph on the bottom of the console screen allows an understanding of the placement and the orientation of the camera and the three instrument arms, in the operative field, which are very helpful.

It is important to keep in mind that this platform is new to the surgical armamentarium and still requires further development. Notably, there is no stapler, suction, or vessel sealer currently available. While these problems can be worked around, they represent significant limitations for this device and transanal robotic procedures. A similar issue was encountered with the development and rollout of the Si and Xi robots, and we anticipate that these instruments will be available in the near future. As these additional tools are supplemented, we believe the SP platform will become increasingly advantageous with serially reproducible results.

Conclusion

While theoretically very appealing, we should all remain mindful that the current state of robotic transanal surgery is still in its early stages. We know, however, that any device that minimizes the difficulty of surgery and improves the ability of a wide array of surgeons to perform the surgery safely improves the effectiveness of that approach. There is no question in our mind that the articulation, vision, and compact efficiency of the SP robot will usher in an expansion of transanal surgical approaches. As this robotic technology is placed in the hands of a large surgeon pool, its ultimate capabilities would be developed for the benefit of patients worldwide. The challenge, as with all new technology, would be to usher in this growth of transanal robotic rectal cancer surgery, with the SP robot, in a responsible manner. Our goal must always be to obtain the best possible outcomes for our patients with the fewest problems encountered in an efficient and cost effective manner. To date we are only just starting on this path, but its future seems bright.