NCT03856671.

Study name	Prophylactic Effect Preoperative Antibiotics With Mechanical Bowel Preparation in SSIs
Methods	Study type: interventional Study design Allocation: randomised Intervention Model: parallel assignment Masking d: no masking is to be conducted in the current study Primary purpose: prevention
Participants	Condition or disease: Surgical Site Infection, Postoperative Complications, Bowel Preparation, Oral Antibiotics, Colorectal Cancer Inclusion criteria Older than 18 years old Undergoing laparoscopic colorectal surgery due to malignancy Exclusion criteria No elective surgery Intra‐abdominal infection Combination of other infectious surgery such as appendectomy, cholecystomy Sever comorbidity such as uncontrolled hypertension and diabetes mellitus Peritoneal implantation and metastasis Radiotherapy history Colorectal surgery due to benign lesions Allergic to antibiotics or PEG Preoperative dermatosis may interfere wound healing Long time application of corticosteroid Autoimmune disease may affect wound healing Patients refuse to enrol Target sample size: 360
Interventions	Treatment arms Experimental: oral antibiotics+mechanical bowel preparationLiquid diet and polyethylene glycol with 2L water was administrated orally 1 day before surgery. A combination of neomycin 1g and metronidazole 0.2g every 6 hours was also administrated. Enteroclysis was conducted for patients on surgical morning. No Intervention: simple mechanical bowel preparation. Only liquid diet and polyethylene glycol with 2L water was administrated orally 1 day before surgery. Enteroclysis was conducted for patients on surgical morning.
Outcomes	Primary outcome Surgical site infection incidence [Time Frame: 30 days after surgery] Secondary outcomes Antibiotics associated complications [Time Frame: 30 days after surgery] Length of hospital stay after surgery [Time Frame: 30 days after surgery] Bowel recovery time [Time Frame: 7 days after surgery] Other postoperative complications [Time Frame: 30 days after surgery]
Starting date	Date of registration: February 27, 2019 Actual Study Start Date: January 17, 2019 Estimated Primary Completion Date: June 30, 2021 (Last Update Posted: February 5, 2020) Recruitment Status: Recruiting (Last Update Posted: February 5, 2020)
Contact information	Contact person: Purun Lei Affiliation: The Third Affiliated Hospital of Sun Yat‐Sen university Country of origin: China
Notes	Ethics approval: ‐ Source of funding: ‐