Supplementary Material for: Association of Anuria and Ultrafiltration Rate With Mortality in Chronic Hemodialysis: A 10-Year Cohort Study

Introduction:
Residual renal function is an important determinant of outcomes in patients undergoing chronic hemodialysis (HD). However, data on the long-term associations of anuria and ultrafiltration rate (UFR) with mortality remain limited, particularly in Latin American populations. This study aimed to identify factors associated with anuria and evaluate the associations between anuria, UFR, and long-term mortality in patients receiving maintenance HD.

Methods:
We conducted a retrospective cohort study that included adult patients undergoing maintenance HD at a single center. The patients were followed up for up to 10 years. Data on baseline demographic, clinical, and dialysis-related variables were collected. Cox proportional hazard models were used to assess the association with all-cause mortality. Multiple sensitivity analyses were performed using alternative covariate selection strategies and the exclusion of selected patient subgroups to evaluate the robustness of the findings.

Results:
Ninety patients were included (mean age 59.1 ± 15.6 years, 26.7% anuric). Anuric patients had longer dialysis vintages and a higher UFR than non-anuric patients. During follow-up, 60% of the patients died. In multivariate analyses, anuria was independently associated with mortality (aHR 5.24; p<0.001). A higher UFR was also independently associated with mortality, with a 9% increase in risk per 1 mL/kg/h (aHR 1.09; p=0.025). The results were consistent across sensitivity analyses.

Conclusion:
In patients undergoing chronic HD, baseline anuria and a higher UFR were independently associated with increased long-term mortality. These findings suggest that the preservation of residual renal function and optimization of volume management may represent important and potentially modifiable targets for improving long-term outcomes.