J Rheum Dis 2018; 25(2): 116-121  
Is the Serum Uric Acid Level Independently Associated with Incidental Urolithiasis?
Doo-Ho Lim1, Min-ho Kim2, Seokchan Hong3, Yong-Gil Kim3, Chang-Keun Lee3, Seung Won Choi1, Bin Yoo3, Ji Seon Oh4
1Division of Rheumatology, Department of Internal Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, 2Ewha Institute of Convergence Medicine, Ewha Womans University Mokdong Hospital, 3Division of Rheumatology, Department of Internal Medicine and 4Clinical Research Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
Correspondence to: Ji Seon Oh http://orcid.org/0000-0002-0205-6492
Clinical Research Center, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea. E-mail:mdjsoh@amc.seoul.kr
Received: October 11, 2017; Revised: January 1, 2018; Accepted: January 23, 2018; Published online: April 1, 2018.
© Korean College of Rheumatology. All rights reserved.

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Objective. Urolithiasis is one of the manifestations of gout and the risk is higher in gouty patients. On the other hand, an independent association between the urinary stone and serum uric acid (UA) level has not been established. This study examined whether the risk of urolithiasis increases with increasing serum UA level. Methods. Among the people who visited a tertiary hospital from 2010 to 2013, 13,964 individuals who underwent both ultrasonography and a laboratory test were recruited in the study. The risk of urolithiasis on ultrasonography was analyzed in association with the serum UA level by multiple logistic regression analysis with an adjustment for age, sex, body mass index, estimated glomerular filtration rate, and known underlying diseases, including diabetes mellitus and hypertension. Results. Among the 6,743 men (48.3%) and 7,221 women (51.7%), the age was 51.3±13.5 and the serum UA level was 4.5±2.1 mg/dL. Hyperuricemia (>7 mg/dL) was observed in 1,381 cases (9.9%). Urolithiasis was detected by ultrasonography in 608 cases (4.4%). The detection rates of urolithiasis in individuals with hyperuricemia and normouricemia were 5.9% and 4.1%, respectively (p=0.001). Multiple logistic regression analysis showed that individuals with hyperuricemia had a significantly higher risk of urolithiasis (adjusted odds ratio [OR]=1.54; 95% confidence interval [CI], 1.20~1.96; p=0.001). A comparison of the highest with the lowest quartile of serum UA revealed a multivariable-adjusted OR of 3.17 (95% CI, 1.98~5.11) for men and 1.79 (1.08~2.93) for women. Conclusion. These results suggest that individuals with a higher serum UA level have a higher risk of subclinical and clinical urolithiasis.
Keywords: Uric acid, Hyperuricemia, Urolithiasis, Urinary calculi, Gout

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