The variability and dietary dependence of urinary oxalate excretion in recurrent calcium stone formers.

Twenty-two recurrent calcium stone formers had 24-h urinary oxalate excretions on their home diets which were significantly greater than those of 30 normal subjects (0.48 +/- 0.23 mmol/d; mean +/- SD compared with 0.31 +/- 0.11; P less than 0.01). The stone formers also demonstrated marked day to day variability in oxalate excretion indicating that a single normal urinary oxalate measurement did not exclude significant hyperoxaluria at other times. On a hospital diet containing 1000 mg calcium per day, urinary oxalate excretion fell significantly from 0.48 +/- 0.23 mmol/d to 0.32 +/- 0.12; P less than 0.01. As the urinary calcium excretion in and out of hospital was similar, it seems unlikely that low calcium intake at home was responsible for the hyperoxaluria. All patients had recurrent symptomatic stone disease and had been advised to avoid foods rich in oxalate. Whilst poor compliance is a possible explanation for the variability in oxalate excretion, we believe it is more likely that there is an inadvertent intake of oxalogenic precursors in their diet. As normal subjects do not demonstrate hyperoxaluria on similar home diets, stone formers may have a metabolic defect in the handling of these precursors.

Cellulose phosphate and chlorothiazide in childhood idiopathic hypercalciuria.

A calcium loading test performed on seven of eight children with idiopathic hypercalciuria identified the hyperabsorptive form of hypercalciuria in five and renal hypercalciuria in one. The type of hypercalciuria was not identified in the other patient. Three children presented with hematuria without calculus formation. Chlorothiazide reduced the urinary calcium excretion level in two of six patients to the normal range. The addition of cellulose phosphate to chlorothiazide reduced the urinary calcium excretion level to the normal range in those four patients who showed an incomplete response to chlorothiazide alone. There was clinical improvement with cellulose phosphate in another child whose symptoms did not disappear after chlorothiazide had reduced urinary calcium level to the normal range. Cellulose phosphate is effective in children with recurrent stone formation who have shown inadequate response to chlorothiazide.