A reproducible ex vivo model for transanal minimally invasive surgery

Rectal tumors can be excised through a number of minimally invasive transanal techniques including transanal excision, transanal endoscopic microsurgery, and transanal minimally invasive surgery (TAMIS). Specialty training is often required to master the nuances of these approaches. This study aimed to create a reproducible transanal excision training model that is suited for laparoendoscopic techniques.

Frozen porcine rectum and anus with intact perianal skin were commercially obtained. Thawed specimens were then cut to approximately 20 cm in length. The proximal end of the rectum was then everted and suction applied to the mucosa to create pseudopolyps of various sizes (sessile and pedunculated). Larger pedunculated lesions were made by tying the base of the pseudopolyps with 5-0 monofilament sutures to gather more tissue. Methylene blue dye was injected submucosally into the lesions to simulate tattoos. The proximal rectum was then closed with sutures. The model was suspended in a trainer box by clamping the distal end in a ringed clamp and the proximal end to the box. Transanal excisions using TAMIS were then performed. The procedures were done by trained community colorectal surgeons attending courses on transanal minimally invasive surgery.

Both partial- and full-thickness excisions of sessile and pedunculated rectal lesions were successfully performed during simulated TAMIS by trained community surgeons learning this laparoendoscopic technique.

Transanal laparoendoscopic procedures to excise rectal tumors can be successfully and reproducibly performed in an ex vivo porcine anorectal model.