Uric acid is a product of the breakdown of purines from food or the destruction of body cells. Uric acid is normally excreted by the kidneys. Uric acid levels in a single urination or in a 24-hour urine collection are mostly useful in assessing the risk of urate stone containing urates. Results are reported in millimoles per day (mmol/d) for 24-hour collections (preferred) and in micromoles per millimole of creatinine (µmol/mmol creat.) for single urinations.
The risk of calcium stone formation is assessed not only based on uric acid levels in the urine but also based on other factors that contribute to stone formation (dehydration, kidney function, urinary infections, certain medications, and calcium, oxalate, phosphate and cystine levels) or factors that prevent their formation (citrate levels).
Several medications can increase or decrease the quantity of uric acid excreted in the urine. High urine levels may also indicate an overproduction of uric acid, as in the case of leukemia, polycythemia (high number of cells in the blood) or after a diet rich in purines (variety or giblets such as sweetbread, liver and kidney; fish such as anchovies and sardines).