This ultrasound image shows increased echogenicity of the renal medulla (the pyramids are normally hypoechoic to cortex). This appearance is typical of medullary nephrocalcinosis.
Medullary nephrocalcinosis has many causes. The most common causes are hyperparathyroidism, renal tubular acidosis, and medullary sponge kidney. Rarer causes of medullary nephrocalcinosis are papillary necrosis, hypercalcaemia, hypercalciuria, prematurity, and primary hyperoxaluria.
This patient had nephrocalcinosis due to Bartter’s Syndrome, a hereditary disorder of ion transporters.
Reference: Chapman S, Nakielny R. Aids to Radiological Differential Diagnosis. 4th edition. Saunders 2003
Credit: Dr Laughlin Dawes