Metabolic evaluation of nephrolithiasis in patients with medullary sponge kidney.

Seventeen patients with documented medullary sponge kidney and nephrolithiasis underwent metabolic evaluation. These patients constituted 3.6% of our stone-forming population. Fifteen (88%) of 17 were hypercalciuric. The most common abnormality was absorptive hypercalciuria, occurring in 59%. Only three patients (18%) had renal hypercalciuria. None of the patients had primary hyperparathyroidism. Hyperuricosuria occurred together with hypercalciuria in five patients. In two patients, the precise cause of hypercalciuria could not be determined, and in another two patients, no metabolic abnormality could be detected. Thus, the patients with medullary sponge kidney and renal stones had the same spectrum of metabolic abnormalities as the overall population of stone formers. While these patients may theoretically have a greater anatomic propensity to form stones because of their anatomic abnormality, they should be evaluated and treated appropriately for any metabolic defect.