Serum and urine uric acid level may have different predictive value for urinary stone composition: a retrospective cohort study of 718 patients in Chinese population

Purpose We launched a retrospective cohort study to explore the interactions among serum uric acid (UA), urine UA, and stone types. Methods Clinical characteristics of urolithiasis patients in Beijing Tsinghua Changgung Hospital from October 2015 to August 2017 were retrospectively collected. Participants were categorized according to the quartiles of SUA and UUA respectively. Logistic regression model was built to identify the relationship between stone composition and UA level. Cubic spline was fitted to explore the correlation between 24-h urine UA and serum UA. Results 718 hospitalized patients (51.1 ± 14.3 years, male 63.4%) with urinary calculi were included. Higher serum UA is associated with male, alcohol use, multiple serum and urine electrolytes (e.g. potassium, chloride, calcium, phosphorus), and lower estimated glomerular filtration rate. The risk of UA stone and carbonate apatite stone was associated with serum UA while the risk of calcium oxalate (CaOx) stone and ammonium magnesium hexahydrate (AMH) was dependent on urine UA. In the unadjusted model (Model 1), higher risks of UA stones were observed in the third quartile (OR 3.26, 95% CIs 1.63–6.53, P = 0.001) and the fourth quartile (OR 3.55, 95% CIs 1.78–7.08, P < 0.001) of serum UA compared with the first quartile. The risks of carbonate apatite stone were lowered in the third (OR 0.48, 95% CIs 0.31–0.73, P = 0.001) and fourth quartile (OR 0.40, 95% CIs 0.42–0.98, P = 0.042) of serum UA. The risk of CaOx stone was increased in the fourth quartile (OR 2.14, 95% CIs 1.15–3.99, P = 0.017) while the risk of AMH stone was decreased in the third (OR 0.46, 95% CIs 0.22–0.94, P = 0.034) and fourth quartile (OR 0.35, 95% CIs 0.16–0.78, P = 0.009) of urine UA. The elevated risks of UA stones in high levels of serum UA were demonstrated in the adjusted model (Model 2). An M-shaped association was found between serum UA and urine UA in our population. Conclusions Serum UA and urine UA might cast different impact on urinary calculus composition. Proper control of the parameters should be considered based on different predisposing factors in individual patients.