THE URINARY EXCRETION OF OXALIC ACID IN UROLITHIASIS

III. OXALIC ACID IN CONCENTRATED URINE

Abstract

The concentrated urine samples were obtained from 17 patients with oxalate urolithiases and 16 control patients who have the normal renal functions (vasectomy, phimosis, oligozoospermia, testicular tumor, etc.), and were measured for osmolality and oxalic acid as well as calcium and magnesium. The method to concentrate the urine is the same as Fishberg's concentration test, that is, the samples were the urines which the patients voided at morning after their over-night fasting. All calculi from the patients with urolithiases were confirmed to contain calcium oxalate by means of infrared spectra subsequent to the surgical removals. Oxalic acid was quantitatively estimated by the method of Yarbro and Simpson, calcium and magnesium were by the EDTA titration with Dotite NN and Dotite BT as indicators (8, 10), and osmolality was measured by means of Advanced freezing point osmometer.
Oxalic acid in the concentrated urine is shown in Fig. 1. The mean was 4.56mg/dl in controls and was 5.63mg/dl in patients with stones. Fig. 2 shows the ratio of oxalic acid: osmolality of the concentrated urine (Oxal/Osm×1000). The mean of ratios in controls was 5.44 and that of ratios in patients with urolithiases was 6.86. These data may indicate that the oxalic acid contents in the concentrated urines of patients with stones are not so different from those of controls. There is no relationship between the oxalic acid level in the concentrated urine and the 24-hr urinary excretion of oxalic acid (Fig. 3 and 4). The ratio of magnesium: calcium×oxalic acid (Mg/Ca×Oxal) in the concentrated urine is shown in Fig. 5. The mean of this ratio was 0.198 in controls and was 0.143 in patients with urolithiases. This result suggests a decrease of this ratio in the concentrated urine of patient with oxalate urolithiasis.