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Total calcium in the urine
Last reviewed: 19.11.2021
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In metabolic equilibrium, the daily excretion of calcium in the urine corresponds to the absorption of calcium in the intestine. Calcium excretion in the urine depends on the amount of filtered calcium in the glomeruli and tubular reabsorption. Filtration in the glomeruli of ionized calcium and calcium in a complex with low-molecular anions (approximately 60% of the total in the blood serum). The kidneys reabsorb 87-98% of filtered calcium. Reabsorption of calcium occurs passively throughout the nephron. The proximal convoluted tubules reabsorb 60%, the Henle loop 30%, the distal part of the nephron 10% calcium. Reabsorption of calcium in the distal tubules of the kidneys stimulates PTH. To fully understand the metabolism of calcium in the patient's body, it is necessary to study it in the urine.
Reference limits for the release of total calcium in the urine
|
Diet |
Amount of Ca | |
|
Mg / day |
Mmol / day | |
|
Lack of calcium in the diet Calcium consumption is below average The average level of calcium intake (800 mg / day or 20 mmol / day) |
5-40 50-150 100-300 |
0.13-1 1.25-3.75 2.5-7.5 |
Normal mechanisms of homeostasis of calcium prevent hypercalcemia by increasing the release of calcium in the urine. In connection with this, any non-renal-related increase in serum calcium concentration causes an increase in calcium filtration and an increased release of calcium in the urine. An increase in the intake of sodium to the Henle loop and the distal renal tubules (for example, in the administration of furosemide) also leads to an increase in the excretion of calcium in the urine. Hypercalciuria leads to a violation of calcium reabsorption in any part of the nephron. Understanding these mechanisms is important for the treatment of nephrolithiasis associated with hypercalciuria.