Mechanical bowel preparation in elective colorectal surgery: a propensity score-matched analysis of the Italian colorectal anastomotic leakage (iCral) study group prospective cohorts

Retrospective evaluation of the effects of mechanical bowel preparation (MBP) on data derived from two prospective open-label observational multicenter studies in Italy regarding elective colorectal surgery. MBP for elective colorectal surgery remains a controversial issue with contrasting recommendations in current guidelines. The Italian ColoRectal Anastomotic Leakage (iCral) study group, therefore, decided to estimate the effects of no MBP (treatment variable) versus MBP for elective colorectal surgery. A total of 8359 patients who underwent colorectal resection with anastomosis were enrolled in two consecutive prospective studies in 78 surgical centers in Italy from January 2019 to September 2021. A retrospective PSMA was performed on 5455 (65.3%) cases after the application of explicit exclusion criteria to eliminate confounders. The primary endpoints were anastomotic leakage (AL) and surgical site infections (SSI) rates; the secondary endpoints included SSI subgroups, overall and major morbidity, reoperation, and mortality rates. Overall length of postoperative hospital stay (LOS) was also considered. Two well-balanced groups of 1125 patients each were generated: group A (No MBP, true population of interest), and group B (MBP, control population), performing a PSMA considering 21 covariates. Group A vs. group B resulted significantly associated with a lower risk of AL [42 (3.5%) vs. 73 (6.0%) events; OR 0.57; 95% CI 0.38-0.84; p = 0.005]. No difference was recorded between the two groups for SSI [73 (6.0%) vs. 85 (7.0%) events; OR 0.88; 95% CI 0.63-1.22; p = 0.441]. Regarding the secondary endpoints, no MBP resulted significantly associated with a lower risk of reoperation and LOS > 6 days. This study confirms that no MBP before elective colorectal surgery is significantly associated with a lower risk of AL, reoperation rate, and LOS < 6 days when compared with MBP.