The rate of anastomotic leakage after laparoscopic anterior resection（LAR） for medium & low rectal cancer is still high. the transanal drainage tube (TDT) was thought to be useful for deduce the rate. There were several studies, but most of them were not randomized controlled trial (RCT) studies. There was only one RCT study with enough samples, but it was designed for open anterior resection, and the patients underwent diverting stoma were excluded, so there was the selection bias. LAR now is thought to been with the same effect, and it is safe and feasible. So a RCT investigation for the use of TDT for prevention of anastomotic leakage after LAR for medium & low rectal cancer is needed.

Patients were randomly assigned to two groups, the TDT and non-TDT group after the laparoscopic LAR and DST procedure was decided during operation. Randomization was obtained through a computer-generated random number sequence allocation. Surgeon blinding was performed to ensure all the intraoperative decisions made by the surgeon were not interfered with by the grouping. All the operative procedures fully complied with the guideline for the diagnosis and treatment of colorectal cancer and the technique of total mesorectal excision (TME). The preservation of the left colonic artery was judged by the surgeon according to his own experiences and assessment of the patient's conditions. When the anastomosis was accomplished, the discretion of DS construction was made by the surgeon based on assessing the risk factors of AL. Pelvic drainages were used in all cases in this study. After completion of the anastomosis and further DS construction if necessary, the surgeon would be notified to implement the intervention based on the randomizing results.

Inclusion criteria: all consecutive 18 to 80 years old individuals diagnosed as primary rectal adenocarcinoma with the lower edge of the tumor less than 10 cm from the anal verge were considered eligible; with the classification of American Society of Anaesthesiologist (ASA) of I, II, or III; Laparoscopic LAR+ with double stapling technique (DST) was planned to perform for the patients. All the preoperative procedures should comply with the guideline for the diagnosis and treatment of colorectal cancer.

Exclusion criteria: The emergency operation for rectal cancer with obstruction, bleeding, or perforation would be excluded. Patients with inflammatory bowel disease (IBD), familial adenomatous polyposis (FAP), recurrent rectal cancer, or synchronous cancer would not be suitable. Patients with preoperative radiotherapy were excluded. Patients who underwent other types of surgeries for rectal cancer, including Hartmann's procedure, abdominoperineal resection (APR), intersphincteric resection ( ISR), et al. were excluded intraoperatively

after the paper published