Patients allocated to MBP will be instructed by the study nurse to prepare their bowel mechanically by drinking 3~4L of polyethylene glycol (Polyethylene Glycol Electrolytes Powder 68.56g; Shenzhen, China) with water before 6pm in the evening the day before the surgery. Patients allocated to NBP were instructed to not prepare the bowel. The receipt of the allocated intervention will be controlled by study nurse asking the patients on the morning of the surgery whether they had acted as instructed by the allocation. This information will be also concealed from treating physicians and surgeons, data collectors, and data analysts, until the primary and secondary outcomes were analyzed. All patients will follow the ERAS protocol. Prophylactic intravenous antibiotics (cephamycin 1000mg) will be given to all patients 30 minutes before skin incision. The prophylactic intravenous antibiotics will re-administered if the surgery lasted longer than 3h from the first antibiotic dose. Surgical skin preparation will involve taking a bath well the night before operation without shaving the hair. Just before skin incision, the area will then washed three times with denatured 80% alcohol to left to dry.
The study type was designed as a prospective multicenter randomized controlled study. The patients will be divided into intervention group (126 cases) and control group, 281 patients were needed for each group and 562 patients would be needed totally to show this difference. The intervention group will not implement mechanical bowel preparation(MBP) before surgery; the control group will receive routine preoperative MBP for oral administration of compound polyethylene glycol electrolyte powder and fasting water. Perioperative complications, intestinal recovery speed and quality of life will be investigated between the two groups.