This measurement is a calculated value representing the percentage of calcium filtered by the kidneys that is subsequently excreted in the urine. It is determined using the concentrations of calcium and creatinine in both urine and plasma samples. The formula involves calculating the ratio of calcium to creatinine in both urine and plasma, then dividing the urine ratio by the plasma ratio and multiplying by 100 to express the result as a percentage. This calculation helps assess how effectively the kidneys are handling calcium.
The determination of this value is significant in evaluating the underlying causes of hypercalcemia (elevated blood calcium) or hypocalcemia (low blood calcium). It assists in differentiating between various renal and metabolic disorders that affect calcium homeostasis. Historically, it has become a useful tool for clinicians to distinguish between familial hypocalciuric hypercalcemia (FHH), a benign genetic condition, and primary hyperparathyroidism, a more serious endocrine disorder that requires different management strategies. Its utility lies in providing a non-invasive method to understand renal calcium handling, impacting diagnostic accuracy and treatment decisions.
