Nephrocalcinosis

Introduction

Nephrocalcinosis is characterised by deposits of calcium salts in the kidney tissue. As usual, this occurs in the interstitium in the medullary areas of the kidney. The condition is often associated with calcium kidney stones (calcium phosphate or calcium oxalate). Otherwise, nephrocalcinosis can also lead to acute or chronic kidney failure or be randomly detected in an x-ray examination. Nephrocalcinosis can have different causes and the prognosis of the kidneys is based on the underlying cause.

Causes

Nephrocalcinosis is due to increased secretion of calcium salts in the urine (calcium phosphate or calcium oxalate). In the medullary areas where the osmolality is high and the concentration of salts exceeds the saturation level for solubility. Citrate is a natural inhibitor of precipitation of calcium salts and hypocitraturia can contribute to the condition.

Table of the most common causes of nephrocalcinosis

Causes Examples

Hypercalciuria with hypercalcemia Primary hyperparathyroidism

Sarcoidosis

Hypervitaminosis D

Hypercalciuria without hypercalcemia Distal renal tubular acidosis

Medullary sponge kidney

Loop diuretics

Congenital tubulopathies

Chronic hypokalemia

Hyperphosphaturia

Hyperoxaluria Congenital: primary

Acquired: fat malabsorption (short bowel syndrome)

Causes	Examples
Hypercalciuria with hypercalcemia	Primary hyperparathyroidism
	Sarcoidosis
	Hypervitaminosis D
Hypercalciuria without hypercalcemia	Distal renal tubular acidosis
	Medullary sponge kidney
	Loop diuretics
	Congenital tubulopathies
	Chronic hypokalemia
Hyperphosphaturia
Hyperoxaluria	Congenital: primary
	Acquired: fat malabsorption (short bowel syndrome)

Histopathology

Tubular, intracellular and interstitial calcium deposits. Interstitial inflammation, interstitial fibrosis and tubular atrophy can be the consequences of calcium deposits. (Picture fom Helge)

Urinalysis

Hematuria can occur simultaneously with kidney stones. Otherwise, the urine is usually normal without proteinuria.

Prognosis and treatment