Medullary nephrocalcinosis (NC), cortical NC

Calcification of renal parenchyma

Medullary NC: Generalized increased echogenicity of renal pyramids with reversal of normal corticomedullary differentiation ± shadowing

Cortical NC: Increased cortical echogenicity ± acoustic shadowing

Noncontrast CT is best imaging modality in adults

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  Exception: CT intravenous pyelogram may be best for medullary sponge kidney given high sensitivity for stones and collecting tubule dilation

US is 1st diagnostic imaging option in infants and children with suspected NC

Renal calculus

Emphysematous pyelonephritis

Other causes of hyperechoic medulla: Metabolic and protein deposition disorders, autosomal recessive polycystic kidney disease

Most common causes of medullary NC are hyperparathyroidism, renal tubular acidosis type 1 (distal), and medullary sponge kidney

Most common causes of cortical NC are acute cortical necrosis, chronic glomerulonephritis, and oxalosis

Medullary and cortical NC are rare and seen in oxalosis

Oxalosis typically causes both medullary and cortical NC

NC is often associated with urolithiasis

NC is often associated with renal calculi

Look for subtle renal calculi with both color Doppler (twinkling artifact) and confirmation with grayscale (posterior acoustic shadowing)

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  Increase PRF to 60-80 cm/s to distinguish twinkling artifact from aliasing artifact