Relationship between urine specific gravity and the prevalence rate of kidney stone

BACKGROUND: The purpose of this study was to evaluate the relationship between urine specific gravity (USG) and the prevalence rate of kidney stone. METHODS: We conducted a cross-sectional study of adult participants (≥20 years) of the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2008. The USG was divided into three groups: <1.008, 1.008–1.020 and >1.020. Univariate and multivariate logistic regression analysis was used to determine the effect of USG on the prevalence rate of kidney stone. RESULTS: A total of 4,791 patients were included in this study, of which 464 (9.7%) reported a history of kidney stone. Univariate logistic regression analysis showed that age, gender, race, hypertension, diabetes, body mass index (BMI), estimated glomerular filtration rate (eGFR), USG and urine creatinine were closely related to the prevalence of kidney stones. After adjusting for known confounding factors, multivariate logistic regression showed that the prevalence rate of kidney stone increased with the increase of USG (1.008–1.020 vs. <1.008, OR =1.31, 95% CI, 0.09–1.91, P=0.155; >1.020 vs. <1.008, OR =1.71, 95% CI, 1.16–2.54, P=0.007). CONCLUSIONS: The increase of USG was significantly correlated with self-reported kidney stone. This finding helps to identify risk factors for kidney stones as early as possible in the United States.