The effects of sodium citrate and oral potassium citrate on urease‐induced crystallization

OBJECTIVES: To study the effects of citrate on urease-induced crystallization in human urine. MATERIALS AND METHODS: Urine samples were collected from seven healthy volunteers with no history of urinary tract infection or stone disease. Citrate was removed from the urine samples by decomposition with citrate lyase. Citrate was then added to the urine in increasing concentrations. Oral potassium citrate was given to the volunteers and their urine was collected. The samples were incubated with urease and the crystallization induced was observed by the Coulter counter technique, by using an optical microscope and by precipitated material analysis. RESULTS: The initiation of crystallization was markedly delayed by both the addition of citrate to the urine and after the ingestion of citrate. Crystal growth and the resulting precipitation of both calcium and magnesium showed a concentration-dependent reduction when citrate was added up to a concentration of 4 mM. Crystal growth and precipitation of calcium and magnesium were also significantly decreased by oral citrate intake. CONCLUSION: Citrate added to the urine or taken orally markedly delays urease-induced crystallization in human urine.