[Epidemiology of the distribution of pure and mixed uric acid stones in the Novosibirsk region].

INTRODUCTION

According to international studies, the prevalence of uric acid stones in 2023 was 8-10% worldwide. Uric acid stones are considered high-risk for symptomatic recurrence. Uric acid constitutes a frequent component of urinary calculi and may promote calcium oxalate stone formation.

AIM

To assess the prevalence of "pure" and mixed uric acid and urate salt stones among urinary calculi in the Novosibirsk Region.

MATERIALS AND METHODS

We evaluated 987 urinary stones from patients with urolithiasis in the Novosibirsk Region. Data for the period 2020-2023 were provided in anonymized form by INVITRO laboratory. We determined the prevalence of single-component and mixed urinary stones containing uric acid and its salts, alone or in combination with other minerals, stratified by sex and age.

RESULTS

Uric acid stones were identified in 119 cases (80 men, 39 women), accounting for 12.06% of all analyzed stones. Pure uric acid stones presented as anhydrous uric acid in 1 case and as uric acid dihydrate in 4 cases. The majority (n=114) were mixed stones of anhydrous uric acid and uric acid dihydrate. Uric acid stones occurred nearly twice as often in men as in women (80 vs. 39). The prevalence of uric acid stones was highest in men aged 31-70 years and in women aged 41-70 years, declining thereafter in both sexes. Mixed uric acid/urate stones (ammonium urate, sodium urate) were found in 15 patients (10 men, 5 women), representing 1.5% of all urinary stones. In women, these types were found at ages 51-70. In men, the most common type was anhydrous uric acid + sodium urate (8 cases), occurring equally in all age groups above 31 years. One stone comprised anhydrous uric acid + ammonium urate (age 41-50). Calcium oxalate combined with uric acid and urate salts in two- and multi-component stones was observed in 99 cases, predominantly in men (58 cases). Overall, calcium oxalate with uric acid and its salts in various combinations accounted for 10.03%.

CONCLUSION

A study of regional stone-forming patterns is essential for planning healthcare at both national and regional level. The prevalence of uric acid stones underscores the need for widespread implementation of oral dissolution therapy and effective metaphylaxis for uric acid urolithiasis. The frequent co-occurrence of calcium oxalate with uric acid warrants comprehensive metabolic evaluation of patients with pure uric acid stones and mixed uric acid/urate stones. Identifying concomitant metabolic disorders in patients with predominately uric acid stones requires tailored urinary pH targets during oral dissolution therapy to minimize conditions favoring precipitation of uric acid salts and phosphate crystallization.