Determinants on urinary excretion of oxalate and other key factors related to urolithiasis among patients with chronic kidney disease: a single center study

Abstract Purpose Urolithiasis is a known risk factor for chronic kidney disease (CKD). However, how CKD might affect the risk of incidence of urolithiasis is not widely studied. Methods Urinary excretion of oxalate as well as other key factors related to urolithiasis was analyzed in a single center study of 572 patients with biopsy-proven kidney disease. Results The mean age of the cohort was 44.9 years and 60% were males. The mean eGFR was 65.9 ml/min/1.73 m2. Median urinary excretion of oxalate was 14.7 (10.4–19.1) mg/24-h and associated with current urolithiasis (OR 12.744, 95% CI: 1.564–103.873 per one logarithm transformed unit of urinary oxalate excretion). Oxalate excretion was not associated with eGFR and urinary protein excretion. Oxalate excretion was higher in patients with ischemia nephropathy as compared with patients with glomerular nephropathy and tubulointerstitial nephropathy (16.4 vs 14.8 vs 12.0 mg, p = 0.018). And ischemia nephropathy (p = 0.027) was associated with urinary oxalate excretion on adjusted linear regression analysis. Urinary excretion of calcium and uric acid was correlated with eGFR and urinary protein excretion (all p < 0.001), with ischemia nephropathy and tubulointerstitial nephropathy associated with uric acid excretion (both p < 0.01) as well. Citrate excretion was correlated with eGFR (p < 0.001) on adjusted linear regression. Conclusion Excretion of oxalate and other key factors related to urolithiasis was differentially associated with eGFR, urinary protein, and pathological changes in CKD patients. The influence of these intrinsic traits of the underlining kidney disease should be considered when evaluating urolithiasis risk in patients with CKD.