Indocyanine green fluorescence imaging for assessing risk factors of anastomotic leakage after colorectal cancer surgery

INTERVENTION: To assess the blood flow at anastomotic site by comparing a direct vision with that under near infrared light after intravenous infusion of indocyanine green. CONDITION: Colorectal cancer PRIMARY OUTCOME: Is it effective or not to assess blood flow at anastomotic site by indocyanine green fluorescent imaging? SECONDARY OUTCOME: To evaluate predictive value of ICG fluorescent imaging, tumor factors and/or intraoperative factors as a risk factor of anastomotic leakage INCLUSION CRITERIA: Patients who were diagnosed with left‐sided or rectal cancer, and had operation with anastomosis