ABSTRACT
Uric acid is the major excretory product arising from the catabolism of purines. The differing reference ranges for the uric acid concentration in serum in adult males and females, as well as those for children, are given in Table 17.1. Since uric acid has limited solubility in water, it is important that the concentrations of uric acid do not go over these reference ranges, as whatever the cause of hyperuricemia, the net effect is the precipitation of urate and uric acid crystals. The solubility product of uric acid in physiological saline at room temperature is 570 μmol/L. However, this is increased in blood due to effects of protein and counterions on urate solubility, such that concentrations in excess of 570 μmol/L can be tolerated without precipitation occurring. These protective effects do not occur in other body fluids, such as synovial fluid and glomerular filtrate, and uric acid crystals deposit more readily in joints, kidneys, and the urinary tract when the urate concentration exceeds 570 μmol/L in these fluids.
