Renal medullary "rings": possible CT manifestation of hypercalcemia.

Bilateral dense rings in the renal medulla were found on noncontrasted computed tomography in a patient with marked hypercalcemia and suspected primary hyperparathyroidism. The rings were not present on plain radiographs and were obscured on contrasted scans, and may represent occult nephrocalcinosis. Associated findings--renal insufficiency induced by hypercalcemia and interstitial nephritis--may be reversible with early recognition of this CT finding.