Urinary oxalic acid excretion was examined in 61 patients with chronic nephropathies and in 21 patients after renal transplantation with a varying mean glomerular filtration. In both groups of patients a correlation was found between the plasma oxalic acid and serum creatinine and by a hyperbolic correlation between plasma oxalic acid and creatinine clearance. Moreover the authors found a direct correlation between oxalic acid and FEoxalic acid and FE(Na)+, FEH20 and FE1-ascorbic acid in both patient groups. Various chronic nephropathies and treatment in both groups did not affect the revealed correlations. In 13 healthy subjects during the period of maximum water diuresis urinary Na+ excretion did not increase but there was a significant increase of the l-ascorbic acid and oxalic acid excretion. In a group of 8 patients in the polyuric stage of chronic renal failure without dialysis treatment under conditions of increased dietary NaCl intake (15 g/24 h) a significant increase of the urinary Na+ excretion was recorded while the l-ascorbic acid and oxalic acid excretion was unaltered. From the assembled values of the examined biochemical indicators ensues that urinary oxalic acid excretion, similarly as ascorbic acid excretion, depended on water excretion.

Keywords: Adult; Ascorbic Acid /urine/; Creatinine /blood/; Female; Humans; Kidney Failure, Chronic /urine/; Kidney Transplantation; Male; Middle Aged; Oxalates /blood/; Oxalic Acid; Sodium /urine/