According to research published in JAMA Internal Medicine, higher levels of urinary oxalate excretion appear to be independently associated with greater risk for chronic kidney disease (CKD) progression and end-stage renal disease (ESRD).
In this prospective study, researchers assessed 3123 patients with stages II to IV CKD (mean age, 59.1 years; female, 45.3%; white, 45.6%) from the Chronic Renal Insufficiency Cohort study. Patients collected urine samples for 24 hours prior to a study visit and the main outcome was a 50% decline in estimated glomerular filtration rate (eGFR) and ESRD.
Mean eGFR at the time of 24-hour urine collection was 42.9 (16.8) mL/minute/1.73 m2. Median urinary excretion of oxalate of 18.6 mg/24 hours was recorded. Urinary excretion of oxalate inversely correlated with eGFR (r = –0.13; P<.001) and positively associated with 24-hour proteinuria (r = 0.22; P<.001).
During follow-up, 752 individuals reached ESRD; and CKD was observed in 940 patients. Higher oxalate excretion independently increased the risk for both CKD progression and ESRD. Compared with patients in the lowest quintile (<11.5 mg/24 hours), those in the highest quintile of oxalate excretion (27.8 mg/24 hours) had a 33% higher risk for CKD progression (HR, 1.33; 95% CI, 1.04-1.70) and a 45% higher risk for ESRD (HR, 1.45; 95% CI, 1.09-1.93).
Nonlinear association was observed between oxalate excretion and CKD progression and ESRD, with a threshold effect at quintiles 3 to 5 vs quintiles 1 and 2. Higher oxalate excretion was associated with a 32% higher risk for CKD progression (HR, 1.32; 95% CI, 1.13-1.53) and a 37% higher risk for ESRD (HR, 1.37; 95% CI, 1.15-1.63)
“If our results are confirmed, future research on pharmacologic or dietary measures to limit oxalate absorption and/or generation would be required to evaluate whether lowering urinary oxalate excretion is beneficial in CKD,” the authors wrote.
