The goal of this clinical trial is to determine whether closing the pelvic floor peritoneum during laparoscopic radical resection of mid-low rectal cancer can reduce the incidence of postoperative ileus. This study will also assess the impact of pelvic floor peritoneal closure on patient recovery and quality of life after surgery. The main questions it aims to answer are:

1. Can closing the pelvic floor peritoneum reduce the incidence of ileus within 30 days after surgery in patients with mid-low rectal cancer?
2. What is the impact of pelvic floor peritoneal closure on postoperative complications such as anastomotic leakage and pelvic infection?
3. How do the two surgical approaches differ in their effects on patients' postoperative anal function, urinary function, and quality of life?

Researchers will compare two approaches after laparoscopic radical resection for rectal cancer: closing the pelvic floor peritoneum versus not closing it, to observe which method more effectively prevents postoperative ileus.

Participants will:

1. Undergo laparoscopic radical resection with anus preservation for mid-low rectal cancer
2. Receive either pelvic floor peritoneal closure or non-closure treatment based on random assignment
3. Attend regular follow-up visits to evaluate intestinal function recovery and occurrence of complications
4. Complete quality of life questionnaires (EORTC QLQ-C30 scale) at 6 months after surgery

This prospective, multicenter, randomized, open-label, parallel-controlled clinical trial aims to evaluate the efficacy of pelvic floor peritoneal closure in preventing postoperative ileus following laparoscopic radical resection for mid-low rectal cancer. The study is designed as a superiority trial with a target enrollment of 516 patients across multiple tertiary medical centers in China, including the Sixth Affiliated Hospital of Sun Yat-sen University and collaborating institutions.

The study protocol employs a computer-generated randomization sequence (using RandomAlloc software) with allocation concealment to assign eligible participants to either the intervention group (pelvic peritoneal closure using continuous 3-0 absorbable sutures) or the control group (non-closure of pelvic peritoneum). Both groups will receive a pelvic drainage tube on the left side, and all surgical procedures will be performed by experienced surgical teams using standardized laparoscopic TME (total mesorectal excision) techniques.

The primary endpoint is the incidence of prolonged postoperative ileus (PPOI) within 30 days after surgery, defined as intestinal obstruction requiring medical intervention (nasogastric decompression, parenteral nutrition for ≥48 hours, or surgical exploration) with radiological confirmation and specific clinical symptoms. Secondary endpoints include postoperative recovery parameters (time to first flatus/defecation, length of hospital stay), surgical metrics (operation time, intraoperative blood loss), postoperative complications assessed using the Clavien-Dindo classification system, and quality of life evaluation at 6 months postoperatively using the EORTC QLQ-C30 questionnaire.

Sample size calculation was based on an estimated PPOI rate of 12% in the control group and 5% in the intervention group, with a one-sided alpha of 0.025, 80% power, and accounting for a 5% dropout rate. Statistical analysis will follow both intention-to-treat (ITT) and per-protocol (PP) principles, with appropriate methods for different data types (t-tests for continuous variables, chi-square tests for categorical variables, and Kaplan-Meier analysis with Log-rank test for time-to-event outcomes).

An interim analysis is planned after approximately 260 patients have been enrolled to evaluate study progress and preliminary efficacy results, with pre-specified stopping rules based on statistical significance after alpha adjustment. Data management follows rigorous quality control procedures, including dual data entry, systematic verification, and secure database locking protocols. All participants will be followed for 3 years from the time of enrollment, with the study period spanning from June 2025 to June 2028.

This investigation addresses a significant clinical controversy in minimally invasive colorectal surgery. While pelvic peritoneal reconstruction has been standard in open rectal cancer surgery, its role in laparoscopic approaches remains uncertain due to technical challenges and limited high-quality evidence. By providing level I evidence through a rigorous randomized controlled design, this study aims to establish clear clinical practice guidelines for pelvic floor management in laparoscopic rectal cancer surgery, potentially reducing postoperative morbidity and improving patient outcomes.

Inclusion Criteria:

• Age: 18-75 years
• Pathology: Histologically confirmed rectal adenocarcinoma
• Tumor Location: Mid-low rectal cancer (inferior margin ≤10 cm from anal verge)
• Surgical Procedure: Laparoscopic radical resection with sphincter preservation
• Exclusion of Other Cancers: No concurrent or prior multiple primary malignancies
• Organ Function: Adequate hepatic/renal/cardiopulmonary function
• Informed Consent: Patient/legal guardian comprehends the study and provides written informed consent

Exclusion Criteria:

• Concurrent or prior history of malignant tumors.
• Miles procedure or Hartmann's operation.
• Intraoperative failure to open the peritoneal reflection.
• Prior pelvic floor surgery.
• Emergency surgery for bowel obstruction.
• Severe hepatic/renal/cardiopulmonary dysfunction, coagulopathy, or underlying diseases contraindicating surgery.
• History of severe psychiatric disorders.
• Pregnancy or lactation.
• Investigator-determined clinical/laboratory contraindications.