Nephrocalcinosis generally refers to the presence of
calcium salts within renal tissue, but this term is also used radiologically in diagnostic imaging in disease states that also produce renal stones, so that it is not always clear whether it is tissue calcifications or
urinary calculi that give rise to the characteristic appearance of the kidney on x-ray or computed tomography (CT). Recent advances in endoscopic imaging now allow the visual distinction between stones and papillary
nephrocalcinosis, and intrarenal endoscopy can also verify the complete removal of
urinary stones, so that subsequent radiographic appearance can be confidently attributed to
nephrocalcinosis. This report shows exemplary cases of
primary hyperparathyroidism, type I
distal renal tubular acidosis,
medullary sponge kidney, and common
calcium oxalate stone formation. In the first three cases--all being conditions commonly associated with
nephrocalcinosis--it is shown that the majority of calcifications seen by radiograph may actually be stones. In common
calcium oxalate stones formers, it is shown that Randall's plaque can appear as a small
calculus on CT scan, even when calyces are known to be completely clear of stones. In the current era with the use of non-contrast CT for the diagnosis of
nephrolithiasis, the finding of calcifications in close association with the renal papillae is common. Distinguishing
nephrolithiasis from
nephrocalcinosis requires direct visual inspection of the papillae and so the diagnosis of
nephrocalcinosis is essentially an endoscopic, not radiologic, diagnosis.