What is the role of dietary studies in the workup of hypercalciuria?

Updated: Jun 02, 2021
  • Author: Stephen W Leslie, MD, FACS; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Once hypercalciuria has been diagnosed, several follow-up tests should be considered to search for an underlying etiology. If excess dietary intake or gut absorption of calcium is a concern, a simple way to verify or refute this notion is to temporarily limit dietary calcium intake and retest.

After initial history and laboratory testing, including serum and 24-hour urinary chemistries as outlined previously, patients with hypercalciuria undergo a short-term trial of dietary modification. (Patients with hypercalcemia and elevated PTH levels probably have hyperparathyroidism and should be treated appropriately.)

The test diet includes a moderate dietary calcium intake of about 600-800 mg/day. This corresponds to roughly 1 good calcium meal per day and possibly 1 additional dairy snack (eg, 1 glass of milk with a second small dairy serving). Restricting dietary salt, which can increase hypercalciuria, is important. Animal protein should be ingested in moderation (< 1.7 g/kg of body weight daily), and dietary fiber should be increased. Limiting dietary oxalate is also advantageous, to avoid an increase in oxaluria due to the loss of intestinal oxalate-binding sites from the reduction in dietary calcium.

The 24-hour urinary chemistries are repeated while the patient is on this modified diet. The author tests all of the urinary chemistries and not just calcium, because of the possibility of finding new chemical risk factors caused by the dietary changes. If patients have normalized their urinary calcium solely with dietary modifications, they can then be treated successfully with this method. If they still have significant hypercalciuria, patients need medical therapy, such as with thiazides, orthophosphates, sodium cellulose phosphate, or bisphosphonates.

The cause of the failure to control urinary calcium with dietary therapy is not particularly important at this point in therapy, although it most likely is a lack of effectiveness of the prescribed diet or a lack of patient compliance.

Testing should be repeated at periodic intervals to ascertain continued patient compliance and effectiveness. Once a stable, satisfactory urinary calcium level is established, periodic 24-hour urinary testing is not necessary more often than perhaps once a year for monitoring. Difficult or unresponsive cases can be referred to an appropriate expert or tertiary care center for further evaluation and treatment.

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