Effect of dietary control of urinary uric acid excretion in calcium oxalate stone formers and non-stone-forming controls.

BACKGROUND AND
PURPOSE: Hyperuricosuria is a well-recognized risk factor for calcium oxalate urolithiasis. Some studies have demonstrated elevated urinary uric acid excretion in stone formers compared with non-stone-forming controls; nevertheless, these studies were limited by patient consumption of self-selected diets. With the recognition that dietary differences may induce variations in urinary uric acid excretion, we evaluated excretion of this compound in stone formers and controls consuming a standardized diet. SUBJECTS AND METHODS: A standardized formula diet was administered to 65 calcium oxalate stone formers and 61 age-matched non-stone-forming controls. During the 3 days of dietary intervention, 24-hour urine collections were obtained. Mean urinary uric acid excretion indexed to urinary creatinine was calculated for each subject, and the results in the two groups were compared.
RESULTS: Stone-forming subjects did not have an elevation in urinary uric excretion compared with control subjects, with mean indexed urinary uric acid excretions of 337 +/- 64 mg/g of creatinine and 379 +/- 76 mg/g of creatinine, respectively.
CONCLUSIONS: With dietary standardization, there was no observed increase in urinary uric acid excretion in our sampled populations. These findings emphasize the role of dietary factors in urinary uric acid excretion and highlight the potential value of dietary interventions.