First Surgery

1. The inferior mesenteric artery is transected at its root.
2. After mobilization to the levator ani hiatus, surgeons may choose to transect the intestinal tract using a linear cutting stapler under laparoscopy according to the location of the tumor's lower margin. Subsequently, a circular stapler is inserted transanally to perform sigmoid-colorectal anastomosis or sigmoid-anal canal anastomosis.
3. If the tumor is adjacent to the anal canal, an intersphincteric resection (ISR) is required, and hand-sewn end-to-end sigmoid-anal canal anastomosis is completed transanally.
4. All patients in the LAR group undergo a protective stoma, which is placed in the right lower quadrant through the rectus abdominis muscle as a loop ileostomy.

Second Surgery The stoma reversal surgery for patients in the LAR group should be completed 3 to 6 months after the first surgery.

First Surgery

1. Abdominal procedure: The inferior mesenteric artery is ligated at its root. The splenic flexure of the colon is mobilized.
2. After mobilization to the levator ani hiatus and entry into the intersphincteric space, the procedure switches to transanal operation. The full thickness of the rectal wall is incised 1 cm above the lower edge of the tumor.

5. The rectal tumor and sigmoid colon are pulled out transanally. The sigmoid colon is transected approximately 8 cm above the tumor to complete tumor resection. The distal sigmoid colon is pulled out 4-5 cm through the anus, and the four pre-placed marking sutures are secured to fix sigmoid colon to the anal canal stump.

Second Surgery

1. The second surgery for resecting the pulled-out intestinal segment is performed 7-14 days after the first operation. The pulled-out intestinal segment is transected approximately 2 mm caudal to the anal canal stump plane. Subsequently, end-to-end anastomosis is completed.

First Surgery 1. Abdominal procedure: The inferior mesenteric artery is ligated at its root. The splenic flexure of the colon is mobilized. 2. After mobilization to the levator ani hiatus and entry into the intersphincteric space, the procedure switches to transanal operation. The full thickness of the rectal wall is incised 1 cm above the lower edge of the tumor. 5. The rectal tumor and sigmoid colon are pulled out transanally. The sigmoid colon is transected approximately 8 cm above the tumor to complete tumor resection. The distal sigmoid colon is pulled out 4-5 cm through the anus, and the four pre-placed marking sutures are secured to fix sigmoid colon to the anal canal stump. Second Surgery 1. The second surgery for resecting the pulled-out intestinal segment is performed 7-11 days after the first operation. The pulled-out intestinal segment is transected approximately 2 mm caudal to the anal canal stump plane. Subsequently, end-to-end anastomosis is completed.

The primary endpoint of the present study was 3-year stoma-free survival. An endpoint event was defined as all-cause mortality or the establishment of a permanent, non-reversible intestinal stoma, whichever occurred first within the follow-up period. A non-reversible stoma was stipulated as one that remained unclosed at the completion of the 3-year surveillance interval, at the time of loss to follow-up, or upon patient demise. Individuals who remained event-free but were censored owing to incomplete longitudinal ascertainment were incorporated as censored observations in the subsequent survival analytical paradigm.

The full name of LARS grading is Low Anterior Resection Syndrome grading, with its core assessment tool being the LARS score (Low Anterior Resection Syndrome score). This grading system categorizes patients into three levels based on the LARS score: no LARS (0-20 points), mild LARS (21-29 points), and severe LARS (30-42 points). It quantifies the severity of intestinal dysfunction following low anterior resection of the rectum, with higher scores indicating more severe dysfunction.

Both surgical complications should be recorded separately, with documentation including the type and severity of complications. Types include infection (incisional infection, pulmonary infection, urinary tract infection, etc.), hemorrhage, organ dysfunction (e.g., cardiac insufficiency, respiratory failure, renal impairment, etc.), anastomotic leakage, thrombosis (deep vein thrombosis, pulmonary embolism, etc.), gastrointestinal dysfunction (e.g., intestinal obstruction, diarrhea, constipation, etc.), and other adverse events directly or indirectly related to the surgery. The severity of complications is typically assessed using the Clavien-Dindo classification system.