Background: Residual renal function (RRF) influences morbidity, mortality and quality of life in chronic dialysis patients. Few studies have been published on risk factors for loss of RRF in dialysis patients. These studies were either retrospective, performed in a small number of patients, or estimated GFR without a urine collection.
Methods: We analyzed the decline rates of residual GFR (rGFR) prospectively in 522 incident HD and PD patients who had structured follow-up assessments. GFR was measured as the mean of urea and creatinine clearance, calculated from urine collections. The initial value was obtained 0 to 4 weeks before the start of dialysis. The measurements were repeated 3, 6, and 12 months after the start of dialysis treatment. After logarithmic transformation, differences in rGFR changes over time were analyzed using repeated measurement analysis of variance.
Results: Baseline factors that were negatively associated with rGFR at 12 months were a higher diastolic blood pressure (P < 0.001) and a higher urinary protein loss (P < 0.001). Primary kidney disease did not affect rGFR. Averaged over time, PD patients had a higher rGFR (P < 0.001) than HD patients. This relative difference increased over time (P = 0.04). Investigation of possible effects of the dialysis procedure on the decline rate between 0 and three months showed that dialysis hypotension (P = 0.02) contributed to the decline in HD and the presence of episodes with dehydration contributed in PD (P = 0.004).
Conclusions: rGFR is better maintained in PD patients than in HD patients. The associated factors such as a higher diastolic blood pressure, proteinuria, dialysis hypotension and dehydration can either be treated or avoided.