The Impact of Two-Stage Turnbull-Cutait Pull-Through Coloanal Anastomosis on Stoma-free Survival in Low Rectal Anal-preserving Surgery

Inclusion Criteria: 1. Patients with rectal cancer aged 18-75 years confirmed by pathological biopsy as adenocarcinoma; 2. Preoperative abdominal contrast-enhanced CT and pulmonary CT (or PET-CT) showed no evidence of distant metastasis; 3. Preoperative rectal MRI evaluation demonstrated that the tumor was located within 5cm below the anal margin, above the intermuscular groove between the internal and external anal sphincters (anal white line) by 1 cm, and without invasion of the external anal sphincter; 4. For tumors located above the levator ani hiatus, MRI evaluation showed cT1-3, cN0-1, M0, MRF (-); for tumors located below the levator ani hiatus, MRI evaluation showed cT1-2, cN0-1, M0, MRF (-). For patients who received neoadjuvant therapy, tumors above the levator ani hiatus were downstaged to ycT3NxM0 or below, and tumors below the levator ani hiatus were downstaged to ycT2NxM0 or below; 5. Preoperative BMI \< 28 kg/m² 6. Patients underwent radical laparoscopic/robot-assisted total mesorectal excision (TME) or transanal total mesorectal excision (TaTME). Exclusion Criteria: 1. Patients diagnosed with concurrent primary malignant tumors in any other organ or multiple distant colorectal cancers; 2. History of previous open surgery (non-minimally invasive procedures); 3. Failure to undergo preoperative rectal MRI evaluation and chest/abdominal imaging assessment, resulting in incomplete clinical staging of the tumor; 4. Pregnant patients or those with concurrent inflammatory bowel disease; 5. Preoperative patients with complete intestinal obstruction or requiring emergency surgery; 6. Preoperative anticipated multivisceral resection or intraoperative required combined organ resection is indicated.; 7. Recent treatment for other malignancies; 8. Low rectal cancer classified as type IV in the Bordeaux classification system; 9. Intraoperatively confirmed distant metastatic disease 10. Preoperative pathological types of signet ring cell carcinoma, mucinous adenocarcinoma, anaplastic carcinoma, or poorly differentiated carcinoma. Withdrawal Criteria 1. Patients who refuse surgical intervention after randomization. 2. Patients who undergo an abdominoperineal resection (APR) following randomization. 3. Patients who request voluntary withdrawal from the trial at any time throughout the study period.