The investigators propose to use flexible endoscopy combined with transanal total mesorectal resection to further reduce anal injury.

Endoscopic technique has become an indispensable part of Natural orifice transluminal endoscopic surgery (NOTES). However, the upper gastrointestinal tract is easy to cause severe leakage complications, which mainly limits the application of endoscopy in rectum. Herein, investigators propose purse suture closing distal rectum and full-layer incision of the rectal wall using flexible endoscopic from anal to assist in hybrid transanal total mesorectal resection (taTME).Further reduce the damage of anus caused by taTME.

Inclusion Criteria:

1. Age between 18 and 80 years old
2. Confirmed rectal adenocarcinoma cancer pathologically
3. tumor location ≦ 12 cm from the anal margin
4. Willing and able to provide written informed consent for participation in this study

Exclusion Criteria:

1. distant metastasis before surgery
2. more than one colorectal tumor at diagnosis
3. familial adenomatous polyposis
4. recurrent rectal cancer
5. undergo transanal minimally invasive surgery
6. undergo palliative treatment
7. undergo emergency surgery

All patients suitable for transanal endoscopic surgery