The Current Prevalence of Uric Acid Stones － A Retrospective Survey in a Municipal Hospital

• Published in: Gout and Uric & Nucleic Acids Vol. 44; no. 1; pp. 41 - 48
• Main Authors: Honda, Kosuke, Kobayashi, Akimitsu, Sugano, Naoki, Yamamoto, Hiroyasu, Yokoo, Takashi, Kuriyama, Satoru
• Format: Journal Article
• Language: English
• Published: Japanese Society of Gout and Uric & Nucleic Acids 25.07.2020
• Subjects: Hyperuricemia; Renal hypouricemia; Uric acid; Urinary pH; Urolithiasis
• ISSN: 2435-0095
• DOI: 10.14867/gnamtsunyo.44.1_41

Aim: The number of patients with hyperuricemia has steadily risen every year. However, it remains unclear whether the prevalence of urinary stones with uric acid (UA) origin is on the same trend. Therefore, we carried out a survey on UA stones in outpatients with urolithiasis.Methods: A retrospective survey was performed in a single municipal hospital. We enrolled a total of 312 patients diagnosed with urolithiasis during the 8 years observation period. All urinary stones underwent chemical component analysis and were divided into two groups: stones of UA component (UA group), and stones of non-UA component (non-UA group).Results: Component analysis revealed the following; calcium oxalate stones 45.5% (n = 142), calcium phosphate stones 1.9% (n = 6), mixed stones without UA component 46.2% (n = 144), magnesium ammonium phosphate stones 1.6% (n = 5), ammonium urate stones 0.32% (n = 1), pure UA stones 2.6% (n = 8) and mixed UA stones 1.9% (n = 6). Stones with UA origin account for 4.5% (n = 14). Urinary pH was lower in the UA vs. the non-UA group (5.6 ± 0.6 vs. 6.5 ± 0.7, p < 0.01). Furthermore, HbA1c and age were higher in the UA vs. the non-UA group.A male patient in the UA group showed substantially low serum UA level (2.5 mg/dL) with multiple bladder stones, casting a suspicion of hereditary renal hypouricemia.Conclusion: Calcium oxalate and mixed stones constitute approximately 90%. The prevalence of UA stones was 4.5%. The rate appears to remain unchanged over a past decade in Japan.