Comparative Effectiveness and Risks of Bowel Preparation Before Elective Colorectal Surgery.

Objective: The objective of this study was to determine the relationship between bowel preparation and surgical site infections (SSIs), and also other postoperative complications, after elective colorectal surgery. Background: SSI is a major source of postoperative morbidity/costs after colorectal surgery. The value of preoperative bowel preparation to prevent SSI remains controversial. Methods: We analyzed 32,359 patients who underwent elective colorectal resections in the American College of Surgeons National Surgery Quality Improvement Program database from 2012 to 2014. Univariable and multivariable analyses were performed; propensity adjustment using patient/procedure characteristics was used to account for nonrandom receipt of bowel preparation. Results: 26.7%, 36.6%, 3.8%, and 32.9% of patients received no bowel preparation, mechanical bowel preparation (MBP), oral antibiotics (OA), and MBP OA, respectively. After propensity adjustment, MBP was not associated with decreased risk of S SI compared with no bowel preparation. In contrast, both OA and OA MBP were associated with decreased risk of any SSI (adjusted odds ratio 0.49, 95% confidence interval 0.38-0.64; and adjusted odds ratio 0.45, 95% confidence interval 0.40-0.50, respectively) compared with no bowel preparation. OA and MBP OA were associated with decreased risks of anastomotic leak, postoperative ileus, readmission, and also shorter length of stay (all P < 0.05). Bowel preparation was not associated with increased risk of cardiac/renal complications compared with no preparation. Conclusions: The use of MBP alone before elective colorectal resection to prevent SSI is ineffective and should be abandoned. In contrast, OA and MBP OA are associated with decreased risks of SSI and are not associated with increased risks of other adverse outcomes compared with no preparation. Prospective studies to determine the efficacy of OA are warranted; in the interim, MBP OA should be used routinely before elective colorectal resection to prevent SSI.