Inclusion Criteria:  (1)18-80 years of age (2)American Society of Anesthesiologists (ASA) class 1-3 (3)single rectal or sigmoid colon carcinoma confirmed pathologically by endoscopic biopsy (4)planned laparoscopic radical resection (5)Written informed consent  Exclusion Criteria:  previous abdominal tumor surgery women who are pregnant or breast feeding emergency patients with obstruction or perforation T4b cancer evaluated by CT or MRI or endoscopic ultrasonography pelvic or distant metastasis T1 cancer planned local excision allergic constitution patients