Implementation of a Structured Perioperative Checklist-Based Standardization Process and Early Postoperative Outcomes After Bariatric Surgery: A Single-Center Retrospective Pre–Post Cohort Study

Background/Objectives: Structured perioperative checklists may standardize bariatric surgical care, but their association with early clinical outcomes remains uncertain. This study compared 30-day postoperative outcomes before and after implementation of a structured perioperative checklist and characterized complications by type and Clavien–Dindo severity. Methods: This single-center retrospective pre–post cohort study included patients undergoing primary bariatric surgery from June 2024 through December 2025. The checklist was prospectively introduced on 29 July 2024. Cohort identification, data extraction, outcome classification, and comparative analyses were performed retrospectively. Forty patients were included in each cohort. The primary outcome was any 30-day postoperative complication; secondary outcomes included complication severity, intensive care unit admission, and length of hospital stay. Checklist implementation was assessed on the basis of documented completion; item-level adherence to individual perioperative measures and corrective actions prompted by checklist responses were not assessed. Accordingly, the intervention evaluated in this study represents implementation of a structured checklist-based documentation and care-standardization process rather than verified adherence to individual checklist components. Results: Complications occurred in 4 of 40 patients (10.0%) in the checklist group and 9 of 40 (22.5%) in the non-checklist group (relative risk, 0.44; 95% confidence interval, 0.15–1.33; p = 0.13). Minor complications occurred in 7.5% and 15.0%, respectively, and major complications in 2.5% and 7.5%, respectively. The study was underpowered to reliably detect a between-group difference in the observed magnitude in 30-day complication rates; therefore, this comparison should be interpreted as exploratory. Median hospital stay was shorter in the checklist group (3 days; interquartile range, 2.5–4.0) than in the non-checklist group (4 days; interquartile range, 3.0–6.0; Mann–Whitney U = 398; p < 0.001). Intensive care unit admission occurred in 7.5% and 17.5%, respectively (p = 0.31). Given the sequential, non-overlapping study periods, the observed difference in length of stay cannot be separated from secular changes in clinical practice, discharge processes, institutional factors, or surgical-team experience. Conclusions: Checklist implementation was temporally associated with a shorter postoperative length of stay, whereas the observed reduction in 30-day complications did not reach statistical significance. Because the cohorts were treated during sequential, non-overlapping periods, these differences cannot be attributed independently to checklist implementation. The findings should therefore be considered exploratory and hypothesis-generating.