Effect of Proteinuria and Glomerular Filtration Rate on Renal Outcome in Patients with Biopsy-Proven Benign Nephrosclerosis

BACKGROUND Reduced estimated glomerular filtration rate (eGFR) and proteinuria are risk factors for end-stage renal disease (ESRD), of which benign nephrosclerosis is a common cause. However, few biopsy-based studies have assessed these associations. METHODS We performed retrospective cohort study of 182 Japanese patients who underwent renal biopsy from June 1985 through March 2014 and who were diagnosed with benign nephrosclerosis. Competing risk regression analyses were used to investigate the effect of eGFR and proteinuria levels at the time of renal biopsy on the risk for renal events (ESRD or a 50% decline in eGFR from baseline). RESULTS During a median 5.8-year follow-up, 63 (34.6%) patients experienced renal events. The incidence of renal events increased with lower baseline eGFR and greater baseline proteinuria levels. After adjustment for baseline covariates, lower eGFR levels (subhazard ratios [SHRs], 1.30; 95% confidence interval [CI], 1.01-1.67, per 10 mL/min/1.73 m2) and higher proteinuria levels (SHR, 1.52; 95% CI, 1.23-1.87, per 1.0 g/day) at the time of renal biopsy were associated independently with higher risk for renal events. Lower levels of serum albumin (SHR, 2.07; 95% CI, 1.20-3.55 per 1.0 g/dL) were also associated with renal events. Patients with both eGFR <30 mL/min/1.73 m2 and proteinuria ≥0.5 g/day had a 26.7-fold higher risk (95% CI, 3.97-179.4) of renal events than patients with both eGFR ≥60 mL/min/1.73 m2 and proteinuria <0.5 g/day. CONCLUSIONS Reduced eGFR and increased proteinuria as well as lower serum albumin at the time of renal biopsy are independent risk factors for renal events among patients with biopsy-proven benign nephrosclerosis.