There are limited data comparing the outcomes of preoperative oral antibiotic bowel preparation (OBP) and mechanical bowel preparation (MBP) in colorectal surgery. We sought to identify the relationship between preoperative bowel preparations (BP) and postoperative complications in colon cancer surgery.

The NSQIP database was used to examine the clinical data of colon cancer patients undergoing scheduled colon resection during 2012 to 2013. Multivariate regression analysis was performed to identify correlations between BP and postoperative complications.

We evaluated a total of 5,021 patients who underwent elective colon resection. Of these, 44.8% had only MBP, 2.3% had only OBP, 27.6% had both MBP and OBP, and 25.3% of patients did not have any type of BP. In multivariate analysis of data, MBP and OBP were not associated with decreased risk of postoperative complications in right side (adjusted odds ratio [AOR] 0.80, 0.30, p = 0.08, 0.10, respectively) or left side colon resections (AOR 1.02, 0.68, p = 0.81, 0.24, respectively). However, the combination of MBP and OBP before left side colon resections resulted in a significantly decreased risk of overall morbidity (AOR 0.63, p < 0.01), superficial surgical site infection (AOR 0.31, p < 0.01), anastomosis leakage (AOR 0.44, p < 0.01), and intra-abdominal infections (AOR 0.44, p < 0.01).

Our analysis revealed that solitary mechanical bowel preparation and solitary oral bowel preparation had no significant effects on major postoperative complications after colon cancer resection. However, a combination of mechanical and oral antibiotic preparations showed a significant decrease in postoperative morbidity.