Excretion of 4-pyridoxic acid and oxalic acid in patients with urinary calculi.

Urinary excretion of 4-pyridoxic acid and oxalic acid was investigated in 75 patients with urinary calculi and in 50 normal subjects on regular diet. Mean excretion of 4-pyridoxic acid was 0.85 and 0.90 mg per day, respectively, and mean excretion of oxalic acid was 27.5 and 28.0 mg per day, respectively. Statistically there was no difference between the two groups in 4-pyridoxic acid excretion or in oxalic acid excretion. There was a weak positive correlation between the urinary excretion of 4-pyridoxic acid and oxalic acid. Patients who were on ascorbic acid supplementation during the urine collection period excreted increased amounts of oxalic acid. It was concluded from this investigation that most patients with urinary calculi had 4-pyridoxic acid excretion and oxalic acid excretion within normal limits. Low 4-pyridoxic acid values were not combined with high excretion values of oxalic acid, and the nutritional state of vitamin B6 in patients with urinary calculi was assumed to be satisfactory in order to control the endogenous oxalic acid production. The significance of high excretion values of 4-pyridoxic acid and oxalic acid is discussed.