The clinical significance of assessment of serum calcium oxalate saturation in the hyperoxaluria syndromes

Estimating calcium oxalate saturation (βCaOx) in body fluids is proposed as a simple and reproducible procedure to assess the risk of systemic oxalosis in several clinical conditions associated with oxalate retention. βCaOx was computerized from the measured concentrations of main serum ions. Accurate assay of serum oxalate was crucial for reliability of βCaOx estimates. However, βCaOx also depended upon changes of calcium and magnesium concentrations. Patients with end-stage renal failure (ESRF) due to primary or enteric hyperoxaluria had βCaOx greater than saturation, whereas this happened in only 10 of 25 and two of 24 of those with oxalosis-unrelated ESRF. Bony content of oxalate measured in some of these patients was consistent with these results. In patients with maintained renal function βCaOx was inversely related to glomerular filtration rate, but the slope was steeper in patients with than in those without hyperoxaluria and βCaOx reached saturation at earlier stages of renal insufficiency.