Pathophysiology and Treatment of Uric Acid Stones

Abstract

Uric acid is the third most common stone composition and comprises 7 to 10% of all kidney stones sent for analysis. These stones are more common with increasing age and in men. Uric acid stone disease is associated with conditions such as the metabolic syndrome and type 2 diabetes mellitus. Uric acid is produced by the enzyme, xanthine oxidase and is the final product of purine metabolism in humans. Three main factors contribute to the formation of uric acid stones: low urine pH (the most important), hyperuricosuria (rare, includes conditions such as myeloproliferative disorders and Lesch-Nyhan syndrome), and low urine volume. Uric acid stones appear radiolucent on plain radiographs and are ultimately diagnosed via stone analysis. These stones may be treated with medical expulsive therapy, dissolution therapy, or surgical intervention depending on the size, location, and clinical presentation. Urine pH manipulation therapy with potassium citrate is the first-line treatment for the prevention of uric acid stones and attempts at dissolution. Allopurinol should not be offered as the first-line therapy for uric acid stones. This review contains 3 figures, 1 table and 38 references Key Words: ammonium, diabetes mellitus, epidemiology, management, metabolic syndrome, nephrolithiasis, pathophysiology, potassium citrate, uric acid, urine pH