Evaluation of the patient with nephrocalcinosis for underlying causes

* The diagnosis of nephrocalcinosis can only be made by imaging or, much less often, kidney biopsy. Most cases are diagnosed as an incidental finding during radiographic imaging of the abdomen or chest performed for another indication or for the evaluation of nephrolithiasis.

¶ Medical conditions associated with nephrocalcinosis include primary hyperparathyroidism, medullary sponge kidney, sarcoidosis, and autoimmune disorders. Refer to UpToDate content on risk factors and causes of nephrocalcinosis.

Δ A family history of kidney tubular dysfunction or kidney stone disease may indicate an underlying genetic disorder.

◊ Medications that can increase urinary calcium excretion include loop diuretics, supplemental calcium and vitamin D, and carbonic anhydrase inhibitors.

§ A variety of definitions for "normal" are used for each of these urinary parameters. However, the values for these definitions are arbitrary, and additional data suggest a more linear relation for each of these factors. As an example, the urinary calcium level above which one is considered to be at risk for nephrocalcinosis is not clear, because the relationship between urine calcium and the risk of nephrocalcinosis is likely continuous, similar to the relationship between urine calcium and the risk of kidney stone formation.

¥ Many patients may have more than one urine abnormality (eg, high urine calcium and high urine oxalate). In such patients, the potential causes of nephrocalcinosis for each urine abnormality should be considered.

‡ In patients for whom there is suspicion for an underlying genetic disorder, genetic testing for a monogenic cause of nephrocalcinosis may be useful.

† In some patients with a low serum phosphorus concentration, the 24-hour urine excretion of phosphate level may not be high (ie, above the reference range), even though the fractional excretion of phosphate is higher than expected given the low serum phosphorus concentration.