Determination of oxalic acid clearance and plasma concentration by radioisotope infusion. Results in a family with hyperoxaluria.

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 mumol/l, whereas values of 3.2 and 16.3 mumul/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 mumol/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.