[Application and short-term efficacy of Da Vinci Xi robot-assisted transabdominal division of the rectourethralis muscle in ultra-low anastomosis surgery for low rectal cancer].
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Objective: To investigate the safety and short-term outcomes of Da Vinci Xi robot-assisted transabdominal division of the rectourethralis muscle (TaRUMD) in ultralow sphincter-preserving surgery for low rectal cancer. Methods: This was a retrospective observational study. The inclusion criteria were as follows: (1) male patients aged 18-75 years; (2) pathologically confirmed rectal adenocarcinoma without distant metastasis that could not be radically resected; (3) tumor located ≤3 cm from the anal verge, with the main tumor body on the anterior wall; (4) good preoperative anal function; (5) no invasion of the anal sphincter complex; and (6) American Society of Anesthesiologists (ASA) score ≤3. Exclusion criteria: (1) signet-ring cell carcinoma, mucinous adenocarcinoma, and other poorly differentiated tumors; (2) delayed anastomosis procedures, such as the modified Bacon procedure; (3) preoperative anal sphincter dysfunction; (4) tumor invasion into adjacent organs.The clinical data of 25 male patients with low rectal cancer who underwent Da Vinci Xi robot-assisted transabdominal division of the rectourethralis muscle for ultralow sphincter preservation performed by the same surgical team of the Department of Colorectal Surgery, National Cancer Center / Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College between March and September 2025 were retrospectively collected. The patients had a mean age of (53.2±11.7) years, a mean body mass index (BMI) of (24.7±2.3) kg/m², and a mean distance from the tumor to the anal verge of (2.3±0.2) cm. Intraoperative and postoperative recovery, complications, and 3-month follow-up outcomes were analyzed. Surgical technique: All operations were completed with the Da Vinci Xi robotic system. After division of the main trunk or branches of the inferior mesenteric artery, the rectum was mobilized to the levator ani plane following the principle of total mesorectal excision (TME). The posterior intersphincteric space was exposed at the 4-5 o'clock and 7-8 o'clock positions in the lithotomy position, and the hiatal ligament at the 6 o'clock position was divided to expose the posterior half of the intersphincteric space. The intersphincteric space was then dissected anteriorly in a clockwise direction from the 9 o'clock position on the left side and counterclockwise from the 3 o'clock position on the right side to expose the rectourethralis muscle, which was divided close to the anterior rectal wall using Maryland bipolar forceps, thereby fully exposing the anterior half of the distal intersphincteric space with positive perineal transillumination. Depending on the tumor size and circumferential extent, the distal rectum was divided transabdominally or after eversion, followed by coloanal anastomosis. Results: All 25 male patients with anterior-wall low rectal cancer successfully underwent Da Vinci Xi robot-assisted TaRUMD, with no intraoperative complications such as vascular or nerve injury and no conversion to open surgery. The mean distance from the anastomosis to the anal verge was (1.2±0.3) cm, the mean operative time was (177.0±47.2) minutes, and the mean intraoperative blood loss was (25.2±11.9) ml. Postoperative pathology showed a mean maximum tumor diameter of (30.3±11.7) mm and a median of 12 (8, 20) harvested lymph nodes. Regarding ypT stage, 18 patients (72.0%) had ypT0-2 and 7 (28.0%) had ypT3; regarding ypN stage, 18 patients (72.0%) were ypN0 and 7 (28.0%) were ypN+. All circumferential and distal resection margins were negative. The mean postoperative hospital stay was (7±2) days. Anastomotic leakage was diagnosed within 90 days postoperatively in 11 patients (44.0%), including grade A in 7, grade B in 3, and grade C in 1. Anastomotic leakage occurred in 9 of the 15 patients who received neoadjuvant radiotherapy, in 1 of the 3 who received neoadjuvant chemotherapy, and in 1 of the 7 who received no neoadjuvant therapy. The median follow-up was 12 (9-15) months; one patient with a preoperatively diagnosed pulmonary metastasis that could be radically resected underwent resection of the pulmonary metastasis six months postoperatively, and the remaining patients were alive with no evidence of disease. No pelvic or anastomotic recurrence was observed in the entire cohort. Conclusion: Da Vinci Xi robot-assisted transabdominal division of the rectourethralis muscle with exposure of the anterior half of the intersphincteric space provides a novel, safe and feasible approach for ultralow sphincter-preserving surgery in male patients with anterior-wall low rectal cancer located ≤3 cm from the anal verge.