Nephrolithiasis in gout: prevalence and characteristics of Brazilian patients.

BACKGROUND

The aims of this article were to assess the prevalence of nephrolithiasis and the factors associated with nephrolithiasis in Brazilian patients with primary gout.

METHODS

One hundred twenty-three patients with primary gout were recruited from a tertiary referral hospital in São Paulo, Brazil. All patients underwent ultrasonography and had their clinical and laboratory characteristics assessed.

RESULTS

One hundred fifteen (93.5%) patients were male, with a mean age of 62.9 ± 9.4 years. Twenty-three (18.7%) patients had asymptomatic nephrolithiasis (detected only by ultrasonography), 7 (6.0%) had symptomatic nephrolithiasis (detected by ultrasonography and a positive clinical history), and 13 (10.0%) had a history of kidney stones, but ultrasonography at evaluation did not show nephrolithiasis. Therefore, 35.0% of the patients had nephrolithiasis (detected either by ultrasonography and/or a positive clinical history). Nephrolithiasis was associated with male gender (43 [100%] vs 72 [90%], p = 0.049), the use of potassium citrate (13 [30.2%] vs 0, p <  0.001) and the use of medications for diabetes (10 [23.3%] vs 8 [10%], p = 0.047) and dyslipidemia (15 [34.9%] vs 10 [12.5%], p = 0.003); benzbromarone had an inverse association with nephrolithiasis (21 [48.8%] vs 55 [68.8%], p = 0.030). In patients with and without nephrolithiasis, no differences were found in the laboratory and ultrasonography characteristics, including serum uric acid levels, urinary uric acid excretion and urine pH.

CONCLUSIONS

The prevalence of nephrolithiasis in primary gout was 35.0%, and 18.7% of the patients were asymptomatic. Nephrolithiasis was associated with male gender, diabetes and dyslipidemia. A positive history of nephrolithiasis probably biased the prescription of potassium citrate and benzbromarone.