Volume Matters: Longitudinal Retrospective Cohort Study of Outcomes Following Consolidation and Standardization of Adrenal Surgery

Subspecialization of adrenal surgery through regionalization has not been adequately evaluated. We assessed implementation of subspecialization and the association of regionalization with adrenalectomy outcomes in a community-based setting. In this longitudinal retrospective cohort study, we used an interrupted time series analysis on consecutive adrenal surgeries at Kaiser Permanente Northern California, 2010–2019. The intervention was regionalization of surgery in 2016. Main outcomes include surgical volumes, operative time, length of stay, 30-day return-to-care, and 30-day complications obtained from the electronic medical record. t-Tests and multivariable models were used to analyze time trends in outcomes after accounting for changes in patient and disease characteristics. In total, 850 adrenal surgery cases were eligible. Between 2010 and 2019, the annual incidence of surgery (per 100,000 persons) increased from 2.4 (95% CI 1.9–3.1) to 4.1 (95% CI 3.5–4.8). Average annual surgeon volume increased from 2.4 (95% CI 1.6–3.1) to 9.9 (95% CI 4.9–14.9), while hospital volume increased from 3.5 (95% CI 2.3–4.6) to 15.4 (95% CI 6.9–24.0). Operative time was 34 (23–45) min faster in 2018–2019 compared with 2010–2011. After regionalization, same-day discharges increased to 64% in 2019 (p < 0.0001). The frequency of return-to-care (p = 0.69) and the overall complication rate (p = 0.31) did not change. Regionalizing adrenal surgery through surgical subspecialization and standardized care pathways was feasible and decreased operative time, and hospital stay, while increasing the frequency of same-day discharges without increasing return-to-care or complications.