Oxalic acid concentration in serum measured by isotopic clearance technique. Experience in hyper- and normo-oxaluric subjects.

In a family from which two children suffered from primary hyperoxaluria the renal clearance of (14C) oxalate was studied. The (14C) oxalate/creatinine clearance ratio ranged from 1.76-2.63 (mean: 2.03) and appeared to be independent of glomerular filtration rate (GFR). The calculated plasma oxalate concentrations in normo-oxaluric subjects ranged from 0.1-0.9 mumol/L, whereas in hyperoxaluric subjects values between 3.2-16.3 mumol/L were found. The mean biological half-life of (14C) oxalate was 2.7hr in subjects with normal renal function and increased proportionally with renal functional impairment. Recovery of (14C) oxalate ranged from 87-112% (mean: 101%). All urine (14C) activity was found in the oxalate fraction.