Association between weekend and out-of-hours emergency abdominal surgery and clinical outcomes: an exploratory retrospective cohort study

The “weekend effect” describes worse outcomes for patients treated on weekends compared with weekdays, but its presence in emergency abdominal surgery remains unclear. This study evaluated the impact of weekend and out-of-hours surgery on clinical outcomes. Methods: This retrospective cohort study included consecutive patients undergoing emergency abdominal surgery at a single institution between April 2022 and March 2024. Patients were categorized by surgery timing: weekends, weekday working hours, and weekday out-of-hours. Three analytical approaches were used to assess timing effects. The primary outcome was in-hospital mortality; secondary outcomes included postoperative length of stay, surgical site infection (SSI), and total hospitalization costs. Statistical analyses included the Mann–Whitney U test, chi-square test, and univariate logistic regression. Results: A total of 125 patients were included, with 60.0% undergoing laparoscopic surgery. No significant differences were observed between weekend and weekday groups in patient characteristics, operative variables, or clinical outcomes across all principal comparisons. In-hospital mortality, length of stay, SSI rates, and hospitalization costs were comparable regardless of surgery timing. These findings were consistent across all principal and exploratory comparisons. Conclusions: In this exploratory single-center cohort, we did not identify a statistically significant association between surgery timing and clinical outcomes. However, the limited sample size, low mortality event rate, and absence of robust confounder adjustment preclude conclusions regarding equivalence or absence of a weekend effect.