Uric Acid Threshold That Predicts Kidney Stone Formation Identified

Serum uric acid levels of 10 mg/dL or higher are associated with an increased risk for nephrolithiasis.
Serum uric acid levels of 10 mg/dL or higher are associated with an increased risk for nephrolithiasis.

Individuals with serum uric acid levels of 10 mg/dL or higher have a higher prevalence of kidney stones compared with those who have lower levels, new study findings suggest.

Elevated serum uric acid levels are a known cause of uric acid stones, but the level that accelerates kidney stone formation has been unclear.

The study, by Kong-Sang Wan, MD, PhD, of Taipei City Hospital-Zhongxing Branch, Taiwan, and colleagues, enrolled 120 male patients with newly diagnosed gout and serum uric acid concentrations above 7 mg/dL and no history of kidney stones. Investigators divided patients into 2 groups: patients with serum uric acid levels below 10 mg/dL (group 1, 80 patients) and those with levels of 10 mg/dL or higher (group 2, 40 patients). The time elapsed since gout onset was less than 4 years in both groups.

The prevalence of kidney stones as detected by ultrasonography was significantly higher in group 2 than in group 1 (82.5% vs 6.3%), investigators reported in the Hong Kong Medical Journal. The sensitivity and specificity of a serum level of 10 mg/dL or higher in predicting kidney stones was 87% and 91%, respectively.

The investigators concluded that patients with gouty arthritis and serum uric acid levels of 10 mg/dL or higher should undergo renal ultrasonography to look for stones.

The 2 groups showed no significant differences in mean age (40 years in both groups), the proportion of patients with a body mass index of 30 kg/m2 or higher (6% in group 1 and 4% in group 2), and urinary pH (5.48 in group 1 and 5.39 in group 2).

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