Impact of the Preservation of Residual Kidney Function on Hemodialysis Survival

Key Points Residual kidney function during the first 2 years of hemodialysis treatment is associated with a long-term (>4 years) survival advantage. Incorporating bioimpedance measurements to inform the setting of the postdialysis target weight does not affect patient survival. Background Preservation of residual kidney function (RKF) in dialysis patients has been associated with improved survival. RKF in the BISTRO trial was relatively well preserved, and in this study, we describe its association with survival during the trial and extended follow-up. Methods RKF, measured as the average urea and creatinine clearance (GFR) or 24-hour urine volume, was assessed at baseline; 1, 2, and 3 months; and every three months for up to 2 years in incident hemodialysis patients. Time to event survival data or competing events (transplantation, modality change) was obtained for 50 months after enrollment via data linkage with the UK Renal Registry. Cox proportional hazards regression survival models, including those incorporating change in GFR from baseline as a time-varying variable and joint regression models for longitudinal and survival data (longitudinal models for GFR or urine volume), were used to explore the relationship of RKF preservation with survival. Analyses were adjusted for age, sex, comorbidity, and ethnicity. Results A total of 2919 measures of RKF were made in 387 patients from 32 UK dialysis units. Higher age and comorbidity score were associated with increased mortality in all models. Baseline GFR reduced the risk of death (hazard ratio [HR], 0.918; 95% confidence interval [CI], 0.844 to 0.999) per ml/min per 1.73 m 2 . A greater fall in GFR and urine volume from baseline was associated with a nonsignificant increased risk of death, as visualized on spline plots. In the joint survival models, higher GFR (adjusted HR, 0.88; 95% CI, 0.80 to 0.97) or urine volume (adjusted HR, 0.75, 95% CI, 0.57 to 0.95/L) at any time point was associated with better survival. Conclusions Lower RKF during the first 2 years of hemodialysis is associated with an increased death risk for up to 50 months after dialysis initiation. This adds to a growing body of evidence that interventions to preserve RKF should be developed and tested in clinical trials.