Association of Mechanical Bowel Preparation and Oral Antibiotics Before Elective Colorectal Surgery With Surgical Site Infection

Importance: There has been a resurgence of interest in the use of mechanical bowel preparation (MBP) and oral antibiotics (OAB) before elective colorectal surgery. Until now, clinical trials and meta-analyses have not compared all 4 approaches (MBP with OAB, OAB only, MBP only, or no preparation) simultaneously. Objective: To perform a network meta-analysis to clarify which approach in colorectal surgery is associated with the lowest rate of surgical site infection (SSI). Data Sources: Five electronic databases were searched, including PubMed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, ACP Journal Club. and Database of Abstracts of Review of Effectiveness from database inception to November 27, 2017. Study Selection: Only data from randomized clinical trials were included. Inclusion criteria were RCTs that reported on SSI rates or other complications based on MBP or OAB status. Quality of studies was appraised by the Cochrane Collaboration risk of bias tool. Data Extraction and Synthesis: The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Main Outcomes and Measures: Total, incisional, and organ/space SSI rates. Secondary outcomes included rates of anastomotic leak, mortality, readmissions/reoperations, urinary tract infection, and pulmonary complications. Results: Thirty-eight randomized clinical trials among 8458 patients (52.1% male) were included, providing 4 direct comparisons and 2 indirect comparisons for 8 outcome measures. On Bayesian analysis, MBP with OAB vs MBP only was associated with reduced SSI (odds ratio OR, 0.71; 95% equal-tail credible interval CrI, 0.57-0.88). There was no significant difference between MBP with OAB vs OAB only (OR, 0.95; 95% CrI, 0.56-1.62). Oral antibiotics without MBP was not associated with a statistically significant reduction in SSI compared with any other group (except for a risk reduction in organ/space SSI when indirectly compared with no preparation) (OR, 0.13; 95% CrI, 0.02-0.55). There was no difference in SSI between MBP only vs no preparation (OR, 0.84; 95% CrI, 0.69-1.02). Conclusions and Relevance: In this network meta-analysis of randomized clinical trials, MBP with OAB was associated with the lowest risk of SSI. Oral antibiotics only was ranked as second best, but the data available on this approach were limited. There was no difference between MBP only vs no preparation. In addition, there was no difference in rates of anastomotic leak, readmissions, or reoperations between any groups.