It is a multicenter, prospective, and randomized controlled clinical study of patients with mid- or low- rectal cancer who received laparoscopic TME surgery aims to explore whether the application of near infrared-indocyanine green imaging system can evaluate the anastomotic blood perfusion accurately, and optimize the surgical procedures, or even reduce the incidence rates of postoperative anastomotic leakage in mid- or low- rectal cancer patients.

In total mesorectal excision of rectal cancer, accurate assessment of rectal anastomotic blood supply is crucial: for insufficient anastomotic blood supply is an important cause of postoperative anastomotic leakage, and once anastomotic leakage occurs, the perioperative mortality rate of patients is reportedly 16%. In the past, the assessment of anastomotic blood supply mainly depended on the experience of the surgeon and lacked objective and accurate assessment methods. In recent years, the application of near-infrared fluorescence laparoscopic imaging technology has provided a new way to accurately evaluate anastomotic perfusion. At present, the technology has been applied to evaluate anastomotic blood supply in colorectal cancer surgery worldwide, and its safety and reliability have been confirmed. However, whether the application of this technology can reduce the incidence of anastomotic leakage after total mesorectal excision for rectal cancer and thus benefit patients still needs high-level evidence-based medical evidence support with multi-centers and large samples.Thus, a multicenter, prospective, and randomized controlled clinical study of patients with mid- or low- rectal cancer who received laparoscopic TME surgery was intend to conduct to explore whether the application of near infrared-indocyanine green imaging system can evaluate the anastomotic blood perfusion accurately, and optimize the surgical procedures, or even reduce the incidence rates of postoperative anastomotic leakage in mid- or low- rectal cancer patients.

Inclusion Criteria:

• The age was over 18 years at the time of diagnosis;
• Diagnosis of rectal carcinoma and was confirmed by preoperative pathology;
• MRI was performed before operation, and the distance between the lower margin of tumor and the anal margin was no more than 10cm;
• The colon-rectum or colon-anus anastomosis was performed by laparoscopic TME operation
• The "spleen area" was not free during the operation
• Baseline clinical tumor stage TNM Ⅰ-Ⅲ phase: cT1-4N0-2M0 （AJCC-8 version）;

Exclusion Criteria:

• Allergic to ICG or iodine;
• Patients with intestinal obstruction, intestinal perforation, intestinal bleeding who need emergency operation;
• Patients requiring combined organ resection that the tumor involves adjacent organs;
• Patients with recurrence of tumor or distant metastasis;
• Patients with multiple colorectal cancer;
• Patients with history of inflammatory bowel disease or familial adenomatous polyposis;
• Patients who have participated in or are participating in other clinical trials in the past four weeks;
• Patients that ASA level is larger than III;
• Physical condition: Patients with KPS less than or equal to 60 points or ECOG larger than or equal to 2 points;
• Patients with hepatic dysfunction and MELD larger than 12 points;
• Patients with a history of serious mental illness;
• Pregnant or lactating women;
• Patients who are improper to participate in the study in the opinion of the researchers.