What is renal leak hypercalciuria?

Updated: Apr 23, 2019
  • Author: Stephen W Leslie, MD, FACS; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Renal leak hypercalciuria occurs in about 5-10% of calcium-stone formers and is characterized by fasting hypercalciuria with secondary hyperparathyroidism but without hypercalcemia.

The etiology is a defect in calcium reabsorption from the renal tubule that causes an obligatory, excessive urinary calcium loss. This results in hypocalcemia, which causes an elevation in the serum PTH. This secondary hyperparathyroidism raises vitamin-D levels and increases intestinal calcium absorption. Essentially, this means that, even in cases of undeniable renal leak hypercalciuria, an element of absorptive hypercalciuria can be present.

The diagnosis is relatively easy. Any patient who fails to control their excessive urinary calcium on dietary measures alone and who demonstrates relatively high serum PTH levels without hypercalcemia or hypophosphatemia probably has renal leak hypercalciuria.

The ratio of calcium to creatinine (in mg/dL) tends to be high in renal leak hypercalciuria (> 0.20), and the occurrence of medullary sponge kidney is more likely than in other types of hypercalciuria.

Renal leak hypercalciuria is generally not amenable to therapy with dietary calcium restrictions, because of the obligatory calcium loss, which can easily lead to bone demineralization, especially if oral calcium intake is restricted.


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