Arezzo 2021.

Study characteristics
Methods	Study design: parallel‐group randomised trials Duration of trial: July 2019 to June 2020 Duration of follow‐up: patients were followed for at least 30 days after surgery Country of origin: Italy
Participants	Baseline characteristics Number randomised: 204 participants Number analysed: 204 participants Number eligible and included in this review: 50 Only study patients who underwent preoperative mechanical bowel preparation were included in the meta‐analysis. Intervention: MBP+oAB Number of participants [n]: 26 Age [years; mean (SD)]: 69 (10) Gender [male/female; n]: 18/8   Control: MBP Number of participants [n]: 24 Age [years, mean (SD)]: 68 (13) Gender [male/female; n]: 15/9   Inclusion criteria  Quote: "Patients who were scheduled for colorectal resection in participating centers for any indication (cancer, chronic diverticulitis, inflammatory bowel disease), > 18 years old and in general health condition permitting general anesthesia (ASA, American Society for Anaesthesiology classification I–III) were eligible for inclusion Open, laparoscopic, laparoscopic‐assisted, or laparoscopic converted to open were all suitable techniques, as well as any mechanical bowel preparation as indicated by each centre." Exclusion criteria Quote: "Emergency surgery; appendectomy; primarily urological/gynaecological or vascular procedure; diagnostic laparotomy/laparoscopy without intestinal resection; surgery involving multi‐visceral surgery (e.g. pelvic exenteration); contraindication for MBP; allergy to used drugs; patients who refuse to participate in the study; patients with intra‐abdominal sepsis before surgery (abscess); patients who received antibiotics for any reason within two weeks prior to surgery; patients who do not comply strictly with the assigned prophylaxis regimen; patients who cannot be followed at least four weeks after surgery." Baseline imbalances ‐
Interventions	Comparison Intervention: MBP+oAB Control: MBP   MBP Agent(s): polyethylene glycol Dose per administration: 4000 mL Time(s) of intake: ‐ Route: oral Concomitant medications: ‐   oAB Agent(s): neomycin and bacitracin Dose per administration: 25000 UI and 2500 UI Time(s) of intake: 24, 16 and 8 h before induction of anaesthesia Route:oral Concomitant medications: ‐   Perioperative intravenous antibiotic prophylaxis Agent(s): amoxicillin/clavulanic acid or, in the event of an allergy to penicillin, clindamycin + gentamycin Dose per administration: 2000/200 mg or, in the event of an allergy to penicillin, 600 mg + 2 mg/kg. Time(s) of intake: at the time of induction of anaesthesia, redosing with prolonged surgery   Adherence to regimen: ‐
Outcomes	Outcomes sought in review and reported in trial SSI Anastomotic leakage Mortality Postoperative complications (mild D/C I + II or severe D/C III+IV) Incidence of postoperative ileus Length of hospital stay Side effects of Intervention(s) Outcomes sought but not reported in trial ‐ Outcomes reported in trial but not used in review ‐
Notes	Source of funding: Quote: "Open access funding provided by Università degli Studi di Torino within the CRUI‐CARE Agreement. Authors have nothing to disclose. This study was supported by Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR) under the programme ‘Dipartimenti di Eccellenza ex L.232/2016’ to the Department of Surgical Sciences, University of Torino" Conflicts of interest: quote: "No confict of interest or financial ties to disclose" Ethics approval: The study was approved by the local ethics committee Informed consent: Written informed consent was obtained from all patients Clinical trials registration: NCT04438655 Sample size calculation: "Statistical analysis showed that considering the closest limits of the two CI intervals (13.2 and 8.4%), with a β‐error of 0.20 and a one‐sided α‐error of 0.05, 656 patients were needed per group."