Study on risk factors of urinary stone formation in primary gout patients

Abstract

Objective To explore the risk factors of urinary stone formation in primary gout patients by urinary chemical, serum and urinary biochemical features analysis. Methods All the patients diagnosed as primary gout at Peking University First Hospital from 2009 to 2015 were included in the study. All patients were diagnosed with or without urolithiasis by ultrasound or computed tomography. Their clinical features, baseline urinary metabolic panels and stone composition were analyzed and compared between the two group of patients. Moreover, the risk factors of uric acid stone formation were determined by comparing different composition of stone formation group. Analysis of variance, t-test, chi-square test, spearman's test and logistic regression were used for statistical analysis. Results One hundred and forty-four male gout patients were enrolled in the study among these patients, 48 were with urolithiasis and 96 patients were without urolithiasis. Most (136, 94.4%) patients were under excretion of uric acid. Among 48 gout patients with uric acid urolithiasis, 30(62.5%) patients who had pure uric acid stones, and 18(37.5%) had stones composed of mixed uric acid and oxalic acid.Compared with mixed stone group, the mean age was significantly lower in pure uric acid stone group [(46±13) years vs (60±15) years, t=4.1, P<0.05]; and disease duration was shorter [(42±11) months vs (71±22) months, t=-0.2, P<0.01]. The 24-hour urinary uric acid were significantly higher in the uric acid stone group [(5 205±3 524) μmol/d vs (2 132±1 326) μmol/d, t=3.6, P<0.05]. Also, the mean of both Ccr and Cua were higher [(119±61) ml/min vs (75±39) ml/min, t=3.6, P<0.05; (6.3±3.6) ml/min vs (3.2±2.0) ml/min, t=1.4, P<0.05]. Urinary pH was negatively correlated with uric acid stone in primary gouty patients (r=-0.212, P<0.01); The total excretion of urinary uric acid was positively correlated with uric acid stones formation (r=0.633, P<0.05). High urinary uric acid excretion and Ccr were independent risk factors for uric acid stone formation in primary gout patients. Conclusion Urine pH is negatively correlated with uric acid stone formation. Urinary analysis of 24-hour uric acid and Ccr are risk factors for pure uric acid urolithiasis in primary gout patients. Key words: Gout; Uric acid; Urinary calculi