Laparoscopic colorectal resection with natural orifice specimen extraction will be performed for patients in this group.

Conventional laparoscopic surgery for colorectal cancer will be performed for patients in this group.

After mobilization of bowel and dissection of lymph nodes, a cross clamp was placed distal to the tumor. Distal rectum was transected after fully disinfecting rectal lumen by 10% povidone-iodine. An anvil head attached to circular stapling device was put into abdominal cavity through rectal stump, and put into colon lumen through a longitudinal incision, then the proximal colon was transected in close proximity to the upper pole of incision by a linear stapling device. During specimen extraction though the rectum, a disposable sterile protective cover was used to avoid cancer cell exfoliation and implantation. The rectal opening was reclosed by a linear stapler. End-to-end colorectal anastomosis was performed with a circular stapler using the double-stapling technique.

The early morbidity rate is defined as the event observed during operation and within 30 days after surgery.

Duration of surgery.

Peritoneal fluid samples were collected under sterile conditions at the end of the procedure and sent for gram stain as well as anaerobic, aerobic, and fungal cultures.We assess the contamination rate of peritoneal fluid in the two interventions.