A porcine model of laparoscopic intersphincteric resection for ultra- low rectal cancer

Abstract Objective. To develop a porcine model for laparoscopic intersphincteric resection (ISR) targeting ultra-low rectal cancer. Methods. Six Bama mini-pigs underwent a standard laparoscopic ISR procedure: 1. High ligation and transection of the inferior mesenteric vessels; 2. Exposure and sparing of the pelvic autonomic nerves; 3. Dissection of the rectum down to the levator hiatus; 4. Dissection and transection of hiatal ligament and rectourethralis muscle; 5. Transanal full-thickness circumferential dissection of the anal canal at the level of intersphincteric groove (1cm distal to the dentate line), involving the rectal circular muscle and the conjoint longitudinal muscle; 6. Dissection of the intersphincteric space (ISS) until convergence with the laparoscopically dissected plane with resection of the distal rectum and internal sphincter muscles; 7. End-to-end handsewn coloanal anastomosis. Subsequent to the surgical procedure, ISR modeling was executed. Pathological evaluations were conducted to ascertain the precision of the ISR. Furthermore, postoperative fecal incontinence scores were systematically assessed on a weekly basis throughout a 12-week post-surgery follow-up period. Results. All six pigs survived surgery without conversion to an open approach. There were no occurrences of incisional infection or any surgical complications, including anastomotic leakage, anastomotic bleeding, or ileus. Postoperatively, one pig manifested constipation and three exhibited anal redness, both conditions ameliorating within a week. No erosive ulcers were detected. Notably, all animals exhibited fecal staining on their tails within the first two weeks post-surgery, transitioning to formed feces by the third week. Improvement in defecation frequency was observed after six weeks, with a noticeable reduction in defecation areas after one month. Incontinence scores, evaluated three months post ISR surgery, revealed no significant abnormalities in anal function compared to preoperative assessments. Conclusions. This study established a replicable porcine model for laparoscopic ISR, demonstrating its potential utility in clinical and fundamental research related to ultra-low rectal cancer treatment.