Characteristics

• Renal lithiasis in which calcium deposits form in the renal parenchyma and result in reduced
  kidney function and hematuria.
• Seen with renal ultrasound, or occasionally on plain radiographs of the kidneys.
• Results from an imbalance of stone-promoting and stone-inhibiting factors.
• Incidence in very low-birthweight infants (BW1500g) ranges from 16-64%.
• Risk factors in at risk infants:
• Medications with hypercalciuric effects (furosemide, corticosteroids, aminoglycosides).
• Metabolic acidosis.
• Hypocitraturia.
• Hypercalciuria.
• High urinary oxalate:creatinine ratios.
• High urate:creatinine ratios.

Effects

• Glomerular function: Mean GFR and microalbuminuria in preterm infants is slightly worse
  than in healthy infants.
• Proximal tubule function: Phosphate reabsorption is significantly lower in patients with
  nephrocalcinosis, but plasma phosphate levels are within reference limits; no firm evidence for
  proximal tubular dysfunction.
• Distal tubule function: Urine anion gap of infants with nephrocalcinosis is high, and serum
  bicarbonate levels are low, indicating distal tubular dysfunction.
• Blood pressure: Not higher in infants with nephrocalcinosis, but overall higher in preterm
  infants than in healthy term infants.
• Hypercalciuria: Significantly more hypercalciuria in infants with nephrocalcinosis.

Monitoring/Treatment

• If associated with a medication that causes hypercalciuria, consider trying to stop the
  medication and monitor for resolution.
• Resolves in 75% by 7 years of age.
• Does not appear to have any long-lasting significant health effects.
• Should have:
  • Blood pressure checked at every visit.
  • Yearly renal ultrasounds until resolution occurs.
  • Electrolytes and BUN/Cr checked every 2 years.
• Patients do not need to be followed by renal team unless other issues arise.
• UTI and urolithiasis do not occur any more frequently than in general population.
• Do NOT stop the use of high-calcium containing infant formulas.

Nephrocalcinosis may be caused by a variety of things, including underlying disorders or conditions, medications or supplements, and infections. Causes may include:

• Primary hyperparathyroidism
• Distal renal tubular acidosis (RTA)
• Hypervitaminosis-D states (very levels of vitamin D)
• Other cause of hypercalcemia (increased calcium in the blood)
• Sarcoidosis
• Phosphate supplementation
• Medullary sponge kidney
• Osteoporosis due to immobilization, menopause, aging, or steroids
• Primary (familial) hyperoxaluria, or secondary hyperoxaluria
• Chronic disorders such as Bartter syndrome, primary hyperaldosteronism, Liddle syndrome, and 11-beta hydroxylase deficiency
• Autosomal dominant hypophosphatemic rickets and X-linked hypophosphatemic conditions
• Premature birth

Other causes may include the use of certain medications such as acetazolamide; tuberculosis of the kidney; and infections related to AIDS.

• Multiple endocrine neoplasia type 1 (MEN1)
• Familial distal renal tubular acidosis
• Chronic granulomatous disease
• Primary hyperoxaluria
• Bartter syndrome
• Alport syndrome
• Primary hyperaldosteronism
• Liddle syndrome
• 11-beta hydroxylase deficiency
• Autosomal dominant hypophosphatemic rickets and X-linked hypophosphatemic conditions
• Williams syndrome
• Beta thalassemia