At present, surgical resection is still the main treatment for the potential cure of rectal cancer. Total mesorectal excision (TME) is the gold standard. The traditional laparoscopic or open surgery for some special patients is really difficult, especially for male, prostate hypertrophy, obesity, low tumor and pelvic stenosis patients to expose the gap around the mesorectum and separate to the pelvic floor. While transanal total mesorectal excision (TaTME) approach could be more directly separate the low mesorectum and relatively simple to complete distal rectal transection, which would bring some considerable advantages. Although active learning from abroad, laparoscopic assisted TaTME surgery is now in its infancy in China. It is urgent for clinical studies to obtain the results in China. This multicenter, observational study will help to encourage research in this field and to obtain data on the safety and efficacy of this procedure in Chinese patients with rectal cancer.

Inclusion Criteria:

• adenocarcinoma of the rectum by biopsy
• the lower edge of the tumor from the anal margin less than 10cm according to MRI or rigid endoscopy
• tumor diameter less than 4cm
• baseline clinical stage I-III: cT1-3 N0-2 M0 (AJCC v7)
• tolerable to surgery
• be able to understand and willing to participate in this trial with signature

Exclusion Criteria:

• history of malignant colorectal neoplasia
• recent diagnosis with other malignancies
• patients requiring emergency surgery such as obstruction，perforation and bleeding
• tumor involving adjacent organs, anal sphincter, or levator ani muscle
• muti-focal colorectal cancer
• preoperative poor anal function, anal stenosis, anal injury, or fecal incontinence
• history of inflammatory bowel disease or familial adenomatous polyposis
• participating in other clinical trails
• can not tolerate the surgery
• history of serious mental illness
• pregnancy or lactating women
• preoperative uncontrolled infection
• the researchers believe the patients should not enrolled in

lower rectal cancer patients who are suitable and willing to accept laparoscopy- assisted TME procedure and also agree with the trial