Case #02 Discussion:

At first glance, the anatomy of the kidneys appears normal because of the clear differentiation between cortex, columns, and pyramids. However, the normal appearance of renal pyramids on US is hypoechoic. The relative density of the pyramids is suggested by the shadowing of deeper structures.

Pyramidal nephrocalcinosis carries a long differential, including medullary sponge kidney, hyperparathyroidism, renal tubular acidosis, skeletal demineralization due to a variety of causes, increased intestinal uptake of calcium due to a variety of causes, hyperoxaluria, and renal papillary necrosis. Calcium, filtered from the blood, deposits in the collecting tubules of the renal pyramids, which is echogenic on US.

The clinical picture of elfin facies, hypercalcemia, hypercalciuria, and aortic and pulmonic stenosis is consistent with the diagnosis of William's syndrome, a genetic disorder caused by the deletion of all or part of the long arm of chromosome 7. The hypercalcemia is caused by abnormal sensitivity to vitamin D. William's syndrome causes abnormalities of the dental, renal, nervous, and skeletal systems.