Adding Preoperative Oral Antibiotics to Mechanical Bowel Preparation Reduces Surgical Site Infections in Elective Colorectal Surgery: A Meta-Analysis of Randomized Controlled Trials.

Background and

Objectives

Surgical site infections (SSIs) remain common after elective colorectal surgery. This systematic review and meta-analysis evaluated whether adding oral antibiotic bowel preparation (OAB) to mechanical bowel preparation (MBP) reduces SSIs compared with MBP alone. Materials and

Methods

PubMed, the Cochrane Library, Scopus, and ClinicalTrials.gov were searched for English-language randomized controlled trials published from January 2005 to January 2025. Eligible trials enrolled adults undergoing elective colorectal surgery and compared MBP+OAB versus MBP alone, with standard intravenous prophylaxis in both groups. The primary outcome was overall SSI; secondary outcomes were incisional SSI and organ-space SSI. Risk of bias was assessed with RoB 2, certainty with GRADE, and odds ratios (ORs) were pooled using DerSimonian-Laird random-effects models. The protocol was prespecified but not prospectively registered.

Results

Twelve trials including 4073 patients were included (MBP+OAB, n = 2069; MBP, n = 2004). MBP+OAB reduced overall SSI (OR 0.53, 95% CI 0.37-0.75; p < 0.001; I2 = 62.5%; 95% prediction interval 0.17-1.66), incisional SSI (OR 0.52, 95% CI 0.34-0.80; p = 0.003; I2 = 57.5%), and organ-space SSI (OR 0.63, 95% CI 0.45-0.88; p = 0.007; I2 = 8.3%). The effect was preserved in metronidazole-containing regimens (OR 0.46, 95% CI 0.33-0.65), but this subgroup was exploratory. Excluding high-risk-of-bias studies supported the primary result. Publication-bias assessment was underpowered. Overall and organ-space SSI were moderate-certainty outcomes; incisional SSI was low-certainty, and anastomotic leak was very low-certainty.

Conclusions

In contemporary elective colorectal surgery when MBP is used, adding preoperative OAB probably reduces SSIs. Findings do not establish whether OAB alone is sufficient or whether MBP is necessary; stewardship-relevant outcomes remain insufficiently reported. Funding was provided by ISCIII grant PI25/01285.