To study brushite stone formers (BSF) change in renal function and overall risk of progression to chronic kidney disease (CKD) over time.
A retrospective review of all patients with urolithiasis on stone analysis was performed from 1995-2003. Stones were classified as brushite if they had at least 10% brushite composition on analysis. Patients with a minimum of 6 years clinical follow-up were included in the study. BSF were matched 1:3 to idiopathic calcium oxalate stone formers (CaOxSF) over the same time period. Estimated GFR (eGFR) was calculated using the MDRD equation. CKD was classified by the National Kidney Foundation definition, with grade 3 defined as <60 mL/min/1.73m(2).
We identified 20 BSF who met inclusion criteria and matched to 60 CaOxSF. Pure brushite stones were identified in 13 (65%) patients and 17(85%) had > 50% brushite composition. Median patient age (48 vs 47 years, p=0.82) and baseline eGFR were not different between BSF and CaOxSF (74 vs 69 mLs/min/m2, p=0.68). No patients had stage IV or higher CKD in either group. At median follow-up of 13.6 years, both eGFR (78 vs 74 mL/min/m2, p=0.61) and change in eGFR (0.31 vs 3.2 mL/min/m2, p=0.92) were similar between groups despite the BSF having a higher stone recurrence rate (80% vs 42%, p=0.003). No brushite patients experienced a change in CKD stage.
BSF were not shown to be at increased clinical risk of CKD compared to CaOx SF at long-term follow-up despite more frequent stone recurrence.
Urology. 2016 Sep 12 [Epub ahead of print]
Marcelino Rivera, Chris Jaeger, Daniel Yelfimov, Amy Krambeck
Department of Urology, Mayo Clinic, Rochester, MN., Department of Urology, Mayo Clinic, Rochester, MN. Electronic address: .