Determination of Oxalic Acid Clearance and Plasma Concentration by Radioisotope Infusion

Abstract

The renal clearance of ¹⁴C-oxalate was studied in a family with two children suffering from primary hyperoxaluria. The ¹⁴C-oxalate/creatinine clearance ratio ranged from 1.8 to 2.6 (mean 2.0) and appeared to be independent of the glomerular filtration rate. The calculated plasma oxalate concentrations in the three normo-oxaluric subjects ranged from 0.1 to 0.9 μmol/l, whereas values of 3.2 and 16.3 μmol/l were found in the two hyperoxaluric subjects. In the latter patient, the oxalate production decreased and the clearance increased after vitamin B₆ treatment, resulting in a drop in the oxalate plasma level to 5.3 μmol/l. The apparent distribution volumes, expressed as percentage of body weight, ranged from 30 to 47 % (mean 35). The mean biological half-life of ¹⁴C-oxalate was 2.7 hours in the subjects with normal renal function and increased with impairment of renal function. The recovery of ¹⁴C in the urine ranged from 87 to 112% (mean 101); all ¹⁴C activity was recovered as oxalate.