Oxalate dynamics in chronic renal failure. Comparison with normal subjects and patients with primary hyperoxaluria

In order to separate the effect of oxalate retention in primary hyperoxaluria with renal failure from that of excessive oxalate synthesis and to determine the optimum time for renal transplantation in primary hyperoxaluria, we have studied a series of patients with different degrees of renal failure due to other causes. The results were compared with those obtained in studies on 8 patients with primary hyperoxaluria at different levels of residual overall renal function. In the patients with renal failure unrelated to primary hyperoxaluria, oxalate retention increases rapidly when the glomerular filtration rate (GFR) decreases below about 20 ml X min-1. These results suggest that the reduced renal excretory contribution to oxalate accumulation in primary hyperoxaluria would be expected to be particularly important in this range of GFR. In primary hyperoxaluria, oxalate retention occurs when GFR is only a little below the reference range and measures to remove oxalate from the body should be considered when the GFR falls below 40 ml X min-1 X 1.73 m-2, with a view to their introduction when the GFR is in the range 20-25 ml X min-1 X 1.73 m-2.