Association of Urinary Oxalate Excretion with the Risk of Chronic Kidney Disease Progression

Importance Oxalate is a potentially toxic terminal metabolite that is eliminated primarily by the kidneys. Oxalate nephropathy is a well-known complication of rare genetic disorders and enteric hyperoxaluria, but oxalate has not been investigated as a potential contributor to more common forms of chronic kidney disease (CKD). Objective To assess whether urinary oxalate excretion is a risk factor for more rapid progression of CKD toward kidney failure. Design, Setting, and Participants This prospective cohort study assessed 3123 participants with stages 2 to 4 CKD who enrolled in the Chronic Renal Insufficiency Cohort study from June 1, 2003, to September 30, 2008. Data analysis was performed from October 24, 2017, to June 17, 2018. Exposures Twenty-four–hour urinary oxalate excretion. Main Outcomes and Measures A 50% decline in estimated glomerular filtration rate (eGFR) and end-stage renal disease (ESRD). Results This study included 3123 participants (mean [SD] age, 59.1 [10.6] years; 1414 [45.3%] female; 1423 [45.6%] white). Mean (SD) eGFR at the time of 24-hour urine collection was 42.9 (16.8) mL/min/1.73 m 2 . Median urinary excretion of oxalate was 18.6 mg/24 hours (interquartile range [IQR], 12.9-25.7 mg/24 hours) and was correlated inversely with eGFR ( r  = −0.13, P r  = 0.22, P Conclusions and Relevance Higher 24-hour urinary oxalate excretion may be a risk factor for CKD progression and ESRD in individuals with CKD stages 2 to 4.