Impact of surgical start time on clinical outcomes in urologic surgery: a single-center study of major oncologic surgeries and adrenalectomy.

BACKGROUND: The impact of surgical start time on perioperative outcomes remains controversial, and evidence in urologic oncology is limited. We aimed to evaluate the association between surgical start time and clinical outcomes across major urologic procedures. METHODS: We retrospectively analyzed 2627 patients who underwent major urologic surgeries at a single institution from 2010 to 2025. Patients were categorized into morning (8:00-12:00) and afternoon (after 12:00) groups. Propensity score matching (PSM) was performed to adjust for baseline differences. Perioperative outcomes, including operative time, estimated blood loss, complications, and overall survival, were compared. Linear regression analyses were used to assess the association between surgical start time and operative duration. RESULTS: Before PSM, the morning group included patients with higher perioperative risk, and operative time, estimated blood loss, and overall survival were significantly worse than in the afternoon group. After PSM, 954 patients with balanced baseline characteristics were included in each group. In the matched cohort, estimated blood loss and overall survival were comparable between groups, whereas operative time remained longer in the morning group. Perioperative complication rates were similar between groups. Subgroup analyses demonstrated a consistent pattern across procedures, surgeon experience, and surgical approaches, with operative time shorter in the afternoon group. CONCLUSIONS: Surgical start time was associated with operative duration, with morning procedures taking longer than those in the afternoon. However, surgical start time was not associated with perioperative complications or overall survival. These findings suggest surgical start time may influence operative efficiency but has limited impact on clinical outcomes.