When possible, a two-team approach should be used, where the abdominal and transanal teams work simultaneously during the entire duration of the transanal dissection to shorten the operative time. The improved visualization of deep pelvic structures by combining the view from the abdominal and transanal vantage points may increase the accuracy of the dissection. Table 21-1 includes a list of recommended equipment for taTME.

The two-team approach usually starts with the abdominal portion, with placement of laparoscopic trocars per standard for laparoscopic LAR (Fig. 21-1). The abdominal team proceeds with high ligation of the IMA and inferior mesentery vein, followed by sharp mobilization of the sigmoid and rectosigmoid mesentery. Transanal dissection is then initiated while the abdominal team continues mobilizing the

left colon and performs a complete splenic flexure takedown. Care must be taken to reduce the total CO₂ insufflation pressures and avoid CO₂ retention and embolism. Typically, abdominal pressures are reduced from 15 down to 10 mm Hg, whereas transanal pressures are maintained at 10-12 mm Hg. Leg position in stirrups and the degree of Trendelenburg must be adjusted to optimize exposure for the transanal team and avoid obstructing the abdominal team from maneuvering.

As transanal dissection proceeds cephalad and approaches the level of the peritoneal reflection anteriorly, the abdominal team should have completed left colonic mobilization and started mobilizing the upper portion of the rectum and mesorectum. The abdominal team usually provides the most assistance with the posterior aspect of the TME, namely, mobilization of the posterior mesorectum, which is usually challenging to complete transanally. The steep angle of the sacral promontory usually precludes proximal dissection of the mesorectum by the transanal team, and the abdominal team should preferentially dissect the mesorectum posteriorly toward the pelvic floor. On the other hand, anterior mesorectal mobilization should be preferentially performed entirely transanally, which is where taTME has a unique advantage over any other surgical approach. Anterior mobilization ends with peritoneal entry. Incision of the cul-de-sac is performed by the transanal team under vision by the abdominal team, and followed by the combined transanal and abdominal dissection to complete the TME. The rendezvous approach to complete the TME is a major advantage of taTME. It combines complementary views with angles of retraction and dissection from the abdominal and transanal perspective.

The colon must be delivered transanally for colorectal or coloanal anastomosis. This is facilitated by the abdominal team.

A one-team approach is widely used with excellent outcomes, and is particularly attractive for surgeons who prefer completing the abdominal dissection robotically. A two-team approach is not always practical. The transanal team employs abdominal assistance during critical times; at the time of transanal peritoneal entry, during the rendezvous portion of the case, when completing rectal and mesorectal mobilization, during specimen extraction, and especially during delivery of the colonic conduit transanally. This allows visual confirmation of the lack of tension and ischemia before colorectal or colonanal anastomosis.

Although some centers will initiate taTME procedures with the transanal dissection portion first, especially when attempting pure NOTES taTME, there is consensus among experts that whether a one-team or two-team approach is used, abdominal access should be established first, before transanal dissection. This is based on standard oncologic principles established by Heald et al., which apply to open and minimally invasive TME and include high ligation of the inferior mesenteric vessels before mesorectal dissection and rectal tumor manipulation.

The extent of pelvic dissection depends on the surgeon’s preference; but as a general rule, it is usually carried out until more distal rectal and mesorectal dissection becomes difficult because of poor exposure. Most one-team operators maintain laparoscopic or robotic TME until the peritoneal reflection is reached anteriorly and extend the posterior mesorectal dissection until it becomes obstructed or complicated by limited exposure. At that point, the one-team operator will desufflate the abdomen and will initiate taTME. Upon transanal completion of the TME, assistance may be provided by an abdominal operator for the rendezvous dissection, specimen extraction, and completion of the anastomosis. Alternatively, the same team will return to the abdominal approach to complete any additional steps, including loop ileostomy creation, pelvic drain placement, and abdominal wound closure.

The patient is positioned in high lithotomy position. Whether a one-team or two-team approach is utilized, the steps of transanal dissection are dependent on the exact location of the rectal cancer relative to the dentate line and anorectal ring, because it will affect whether or not ISR is needed. Following confirmation of the exact location of the tumor by digital rectal examination, anoscopy, and/or proctoscopy, a decision is made with respect to the exact level of distal rectal transection needed to ensure a negative distal margin.

The most important first step of the transanal dissection is the occlusion of the rectum with a purse string suture below the tumor. For tumors that are >2 cm above the dentate line, or ≥1 cm above the anorectal ring, that is, when ISR is not needed, the purse string suture is placed to occlude the rectum 0.5-1 cm below the tumor. If the tumor is located <5 cm from the anal verge, the purse string can be placed directly after exposure is achieved with a Lone Star retractor and anoscope. This is followed
by insertion of the transanal platform. It is our preference to use a disposable graduated plastic anoscope, part of a stapled hemorrhoidectomy kit (Fig. 21-2). If the tumor is located ≥5 cm from the anal verge, the transanal platform is inserted first, followed by endoscopic placement of the purse string suture to occlude the rectum. Our preference is to use a 2-0 Vicryl purse string, but a suture of 2-0 Prolene may be used (Fig. 21-3). The purse string suture must be airtight to avoid distension of the proximal colon with CO₂, and spillage of fecal material or tumor cells into the operative field. If upon CO₂ insufflation to 10-15 mm Hg through the rectum, the purse string is leaking, it must be redone or reinforced.

Following purse string occlusion of the rectum, the rectal mucosa is incised with monopolar cautery, followed by full-thickness circumferential incision of the rectal wall (Fig. 21-4). Full-thickness rectal and mesorectal mobilization is carried out using monopolar cautery, with efforts to limit the use of bipolar energy to control troublesome bleeding. Posterior mesorectal dissection must be carried out along the avascular plane between the posterior mesorectum and presacral fascia (Fig. 21-5), and is usually the easiest to achieve because of the easily identifiable anatomic landmarks. The presacral fascia, the shiny mesorectal fascia and the angel hair plane in between, guides the dissection. Care must be taken to avoid dissection too close to the sacrum and injury to the presacral plexus. We suggest starting the taTME dissection posteriorly and then following the TME plane laterally and anteriorly. Anteriorly, dissection is carried out between the rectovaginal fascia or rectoprostatic fascia (Fig. 21-6). Laterally, care must be taken to avoid dissection of the pelvic sidewall during mesorectal mobilization, to preserve the nervi erigente. During the anterolateral dissection of the rectum and mesorectum, care must be taken to avoid injury to the neurovascular bundles bilaterally. It also serves as a landmark for the location of the prostate, if difficulties are encountered during anterior mobilization and identification of the posterior aspect of the prostate. It is important to emphasize that dissection should

be carried out circumferentially and in a sequential pattern, and every effort is made to avoid uneven dissection to circumvent plane distortion, which can disorient and lead the operator astray. Of note, one of the key advantages of the transanal approach is the effect of the pneumorectum, which dissects avascular tissue planes around the rectum. Ultimately, anterior dissection is carried out cephalad until the peritoneal reflection is reached as described earlier. Peritoneal entry is usually performed transanally and under laparoscopic visualization from above (Fig. 21-7). Posteriorly, depending on the angulation of the sacral promontory, transanal dissection can usually be extended toward S1-S2 levels. The remainder of the posterior and lateral dissection is completed using a combined abdominal and transanal approach (Fig. 21-8). An en bloc transanal prostatectomy with urethral anastomosis is feasible as first described by Wexner and Sands at Cleveland Clinic Florida.