Clinical Research Directory

The experimental group underwent the PPISR procedure. The surgical process was as follows: 1. The abdominal team performed the TME procedure, completely resecting the mesorectum at the level of the mesorectum termination line within the levator hiatus. 2. The transanal team completed routine preoperative preparation and disinfection, and located the distal and lateral resection margins of the tumor (with a margin distance ≥5 mm from the tumor boundary), thereby preserving part of the internal anal sphincter and normal intestinal wall tissue. 3. A "U"-shaped dissection was performed cranially along the marking line within the intersphincteric space, meeting the abdominal team at the level of the levator hiatus, as shown in Figure 1. 4. The specimen was removed either transanally or transabdominally. 5. The proximal intestinal segment was trimmed, intestinal anastomosis was performed manually, and the procedure was concluded.

The control group underwent the traditional ISR procedure. The surgical process was as follows: 1. The abdominal team entered the abdominal cavity and mobilized the sigmoid colon and rectum according to the principle of total mesorectal excision (TME). The vessels were ligated at a high position, and the rectum was dissected downward along the presacral space to the level of the levator ani muscle (pelvic floor), fully exposing the distal rectum and the levator ani muscle. 2. The transanal team made a full-thickness circumferential incision in the rectal mucosa slightly above the dentate line (approximately ≥1 cm), entering the intersphincteric groove. A sharp circumferential dissection was performed along this groove to "pull" the rectum (along with its internal sphincter) out from within the external anal sphincter. During this dissection, care was taken to avoid damaging the external sphincter complex and its innervation. 3. When the perineal dissection plane reached the level of