medullary nephrocalcinosis

Nephrocalcinosis can be divided in two subgroups - medullary and cortical. Medullary nephrocalcinosis is much more common, accounting for 95% of nephrocalcinosis. Medullary nephrocalcinosis is an abnormality caused by the deposition of calcium salts into the renal medulla, specifically the distal convoluted tubules. The most common cause in adults is primary hyperparathyroidism, followed by renal tubular acidosis, medullary sponge kidney, and other causes of hypercalcemia (hypercalciuria). Dystrophic medullary nephrocalcinosis can also be seen with papillary necrosis and chronic pyelonephritis. Medullary nephrocalcinosis can also occur in neonates (usually premature) treated with furosemide. Oxalosis (primary or secondary) is a rare cause. Medullary sponge kidney is a congenital disorder entailing renal medullary ductal ectasia. The disease is usually bilateral and often asymptomatic. Symptoms arise from nephrocalcinosis, nephrolithiasis, hematuria, and pyelonephritis. Diagnosis is usually made in adolescence or young adulthood. Life expectancy is normal. Imaging findings in medullary nephrocalcinosis are illustrated in this case. Calcifications can be large or small and are restricted to the renal medulla. Hyperparathyroidism (and other hypercalcemic states) usually causes diffuse medullary calcification; whereas, medullary sponge kidney often causes bulky, clumped calcifications sporadically within the renal papillae (the morphology and location of the calcifications in this case suggest medullary sponge kidney). Medullary sponge kidney can also cause mild renal enlargement, unlike hyperparathyroidism. Clinically, medullary nephrocalcinosis associated with medullary sponge kidney usually causes minimal or no renal dysfunction. In contrast, in hyperparathyroidism, it often accompanies renal insufficiency. Cortical nephrocalcinosis is caused by deposition of calcium into the renal cortex. The most common etiologies are chronic glomerulonephritis and acute cortical necrosis. It is also associated with Alport syndrome, a congenital disorder involving nephritis and deafness.