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Findings: These are echogenic medullary pyramids.

Diagnosis: Medullary nephrocalcinosis

Discussion: Nephrocalcinosis refers to the pathologic deposition of calcium within the wall and lumen of the distal collecting tubules. Medullary deposition of fine calcification in these locations is usually identified.

Predisposing factors to this disease process include furosemide therapy, steroid treatment, renal tubular acidosis, and Williams' syndrome.

Furosemide causes calcium deposition by inhibiting calcium reabsorption in the ascending limb of the loop of Henle. This causes subsequent hypercalciuria. This is a well documented cause of nephrocalcinosis in infants, and is seen considerably in those infants which are premature.

Imaging of nephrocalcinosis may be made by ultrasound which demonstrates an Anderson-Carr type of progression of calcium deposition within the renal parenchyma.

Differential diagnosis of echogenic renal medullary pyramids includes protein deposition, capillary necrosis, infection, vascular congestion, medullary fibrosis, and autosomal recessive polycystic kidney disease.

References:
1. Adams ND, Rowe JC. Nephrocalcinosis. Clinics in Perinatology. 19(1):179-195, 1992.

2. Moxey-Mims MM, Stapleton FB. Hypercalciuria and Nephrocalcinosis in Children.
Current Opinions in Pediatrics. 5(2):186-190, 1993.

3. Blickman JG. Pediatric Radiology, The Requisites. Mosby, 1994.

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