Background: Extralevator abdominoperineal excision (ELAPE) may cause various surgical complications including disruption of perineal wound, perineal hernia and adhesive small-bowel obstruction. Pelvic peritoneum reconstruction could prevent those complications, but it may not always be achievable, especially in patients with severe pelvic fibrosis after neoadjuvant radiotherapy. Previous study has reported the application of the pelvic peritoneum reconstruction using the bladder peritoneum flap in laparoscopic ELAPE. The aim of the study is to evaluate the short-term clinical, technical and safety outcomes of pelvic peritoneum reconstruction using the bladder peritoneum flap in laparoscopic ELAPE.

Methods/Design: This is a single -center prospective cohort study and fulfill the IDEAL 2A stage principle. Rectal cancer patients after neoadjuvant radiotherapy and about to undergo laparoscopic ELAPE will be included. Main exclusion criteria are being complicated with urgent complications, ASA grade > 3 and accompanied with mental illness. Patients suffering rigid pelvis or huge perineal peritoneum defect, and having difficulty in primary perineal wound closure will be considered eligible for the baldder peritoneum flap (BPF) group; corresponding rectal cancer patients will be allocated to the control group. After informed consent, 10 patients are planned to be included in the BPF group. Standard laparoscopic ELAPE with pelvic peritoneal floor reconstruction using BPF are to be performed. The surgical safety is to be evaluated after one-year follow-up. Primary endpoints are the occurrence of intraoperative and postoperative complications of pelvic peritoneum reconstruction after ELAPE. Second endpoints are overall complication rate within 30 days after surgery, extent of small intestine falling down to pelvic cavity, and other follow-up consequences within 1 year after surgery.

In rectal cancers, the overall survival will benefit strongly if a negative incisional margin is reached. In order to pursue a negative margin, APR, expecially the extralevator abdominoperineal excision (ELAPE) which introduced by Holm et al had been used to improve the oncological outcome in T3 and T4 rectal cancer. However, ELAPE could bring a gaping hole beyond repair in the pelvic cavity, leading to serious perineal injury and small bowel dropping into pelvic cavity inevitably. Pelvic peritoneal defects can also result in perineal hernia and adhesive small-bowel obstruction (ASBO).

Reconstruction the pelvic peritoneum could prevent the small intestine adhering to the true pelvis by keeping it in the abdominal cavity, thus decrease the occurrence of ASBO and other perineal complications. However, pelvic peritoneum reconstruction may not always be feasible especially in those patients who had received a neoadjuvant radiotherapy and suffered severe tissue fibrosis or those patients who have a large defect of pelvic peritoneum.

Recently the investigators have reported a novel method to reconstruct the pelvic peritoneum under laparoscope in patients with a rigid pelvis. A bladder peritoneum flap was used to cover the defect of pelvic peritoneum. Previous attempts have proved the feasibility of the pelvic peritoneum reconstruction using the bladder peritoneum flap in laparoscopic ELAPE. This protocol is a further study to verify its short-term clinical, technical and safety outcomes.

The objective of this study is to evaluate the short-term clinical, technical and safety outcomes of pelvic peritoneum reconstruction using the bladder peritoneum flap in laparoscopic ELAPE.

This is a multi-center, prospective development study. The method of PPR using the bladder peritoneum flap in laparoscopic ELAPE is at the development stage. And this protocol fulfills the requirement of IDEAL framework stage 2A. Approval of the ethics committee has been obtained from the ethics committee of West China Hospital, Sichuan University (2019 No. 194). The present study was registered on the clinicaltrials.gov. Any technology amendments will be presented to the institutional review board for further assessment. Benefits and risks of the study will be informed to participants. Only participants who signed an informed consent form and agree to participate will be included in this study. Participants have the right to quit the study at any time without any reason. In emergency circumstances, surgeons have the right to end the study. Data of the details will be stored in a database and published after the trial.

Inclusion Criteria:

• Male patients aged between 18 to 75.
• ASA grade ≤ 3.
• Pathology confirmed as rectal adenocarcinoma;
• Lower rectal cancer with neoadjuvant (chemo)radiotherapy, and an APR was needed;
• The pelvic peritoneum can't be close by direct suture;
• Patients being able to understand the study protocol and willing to participate in the study, providing written informed consent.

Exclusion Criteria:

• Bladder invaded by tumor or primary bladder cancer.
• severe systemic diseases abibuffecting wound healing (e.g. diabetes, liver cirrhosis or immune compromised status like HIV)
• Sensitivity to anti-adhesion barrier.
• Peritoneal implantation.
• History of severe mental illness.
• Continuous systemic steroid therapy recent 1 month