Minimally invasive colorectal surgery is currently well-accepted, with open techniques being reserved for very difficult cases. Laparoscopic colectomy has been proven to have lower mortality, complication, and ostomy rates; shorter median length of stay; and lower overall cost [1] when compared to its open counterpart. This trend is seen in both benign [2] and malignant indications [3–5]. We have sought to transfer these tangible benefits of minimally invasive colonic resection to rectal resection using natural orifice specimen extraction surgery (NOSES), a technique that promises reduction in postoperative pain, wound complications, and incisional hernia risk of a transabdominal extraction.

We present illustrative scenarios of robotic NOSES anterior resection using the da Vinci Xi platform (Intuitive Surgical Inc) in benign diverticular disease and distal sigmoid colon cancer resection.

NOSES in colorectal surgery was first described in the early 1990s [6, 7]. Since then, there have been 41 published case series spanning both malignant and benign indications [8]. The transrectal and transanal route is more common than the transvaginal route, with the former comprising 30 series versus the latter with only 11 series [8]. Three recent meta-analyses comparing transabdominal extraction against NOSES concluded that NOSES was superior in terms of overall postoperative complications, recovery of gastrointestinal function, postoperative pain, aesthetics, and hospital stay [9–11]. However, NOSES was associated with longer operative time, likely due to increased technical complexity associated with an intracorporeal anastomosis [9–11]. There are specific technical differences for achieving natural orifice extraction when compared to transabdominal extraction that may be potential causes of concern and are addressed below.

An intraperitoneal enterotomy and the insertion of a stapler anvil into the abdominal cavity through a natural orifice are potential sources of contamination. Costantino et al. [12] and Wolthuis et al. [13] studied the bacterial positivity rate in peritoneal fluid culture and demonstrated that although NOSES had a higher risk of peritoneal contamination, there were no significant differences in clinical outcomes between the 2 groups. Methods to mitigate intraperitoneal bacterial contamination include perioperative prophylactic antibiotics, preoperative antibiotic bowel preparation, intraoperative peritoneal irrigation, and rectal washout prior to specimen extraction [14]. Furthermore, a recent meta-analysis by Liu et al. [10] concluded that surgical site infection was less common in the NOSES group than in the conventional laparoscopic surgery group, with similar intraabdominal collection rates between the 2 groups. This meta-analysis also demonstrated that NOSES had a lower leak rate (3.6% vs. 5.0%), and other studies have also reported consistent findings [15, 16]. The difference in the leak rate is likely a function of intracorporeal anastomosis, which has key technical advantages of less mobilization and less traction on the mesentery and blood supply, resulting in a more vascularized tension-free anastomosis.

Another important concern is oncological safety, arising from the need for colotomy/rectotomy and specimen extraction through a narrow natural orifice, which may lead to tumor cell seeding and implantation, respectively. In our practice, risk-mitigating steps taken include tumoricidal rectal washout, the insertion of a transanal Alexis retractor, and the utilization of a 15-mm specimen extraction bag. Reassuringly, other studies have confirmed that local recurrence after NOSES is comparable to that after a conventional laparoscopic approach [17], with comparable proximal and distal margin status and lymph node harvest [10]. Lastly, the 5-year disease-free survival and local recurrence rates are comparable between the 2 techniques [17].

With the adoption of colorectal NOSES, there arose a need for the standardization of terminology and techniques, as well as oversight of surgical indications and safety. Therefore, an international consensus statement on NOSES for colorectal cancer was published [14]. This document defines 10 different colorectal NOSES techniques, with various combinations of the type of resection and extraction site. Importantly, the consensus also provides a guideline on what is safe and feasible. In our experience, the patients who would be most suitable for transanal NOSES include patients with a maximum body mass index of 32 kg/m², tumor diameter of 3 cm, and tumors that are in the sigmoid or proximal rectum. Female patients who have a tumor up to 5 cm in size may be appropriate for transvaginal NOSES.

One of the basic requirements for NOSES is an experienced laparoscopic surgeon due to the increased challenges of specimen extraction and gastrointestinal tract reconstruction [14]. These challenges can be partially offset by the benefits of a robotic platform such as the da Vinci Xi. The benefits of the high-definition 3-dimensional system, the ergonomic positioning of the surgeon, the instrument articulation with greater precision, and the absence of tremor might lead to higher accuracy, more precise dissection, a flatter learning curve, all potentially resulting in improved outcomes; not ignoring the fact that most robotic surgeons are themselves already accomplished laparoscopic surgeons. Further studies to evaluate the quality of life and functional outcomes are currently underway.