Description
Nephrocalcinosis refers to the deposition of calcium salts in the renal parenchyma. It is a condition that can be seen in various metabolic, genetic, and renal tubular disorders. This condition can involve the renal cortex (cortical nephrocalcinosis) or the medulla (medullary nephrocalcinosis).
Pathogenesis
Nephrocalcinosis arises due to hypercalciuria, hypocitraturia, or both. Hypercalciuria can result from increased intestinal absorption of calcium, increased bone resorption, or decreased renal tubular reabsorption of calcium. Hypocitraturia can arise from metabolic acidosis, hypokalemia, or renal tubular acidosis. These imbalances cause calcium salt precipitation in the renal parenchyma.
Epidemiology, Risk Factors & Associations
Nephrocalcinosis is associated with multiple conditions, including hyperparathyroidism, renal tubular acidosis, medullary sponge kidney, hyperoxaluria, and hypervitaminosis D. It can also occur in premature infants receiving loop diuretics.
Clinical Features
Nephrocalcinosis may be asymptomatic and discovered incidentally on imaging. When symptoms do occur, they’re often related to the underlying cause, such as renal colic from stone formation or symptoms of renal insufficiency.
Complications
Chronic nephrocalcinosis can lead to renal tubular damage and subsequent chronic kidney disease.
Pathological Features
Histopathology
- Microscopic examination of renal biopsy specimens can demonstrate calcium deposits in the renal tubules and interstitium.
Biochemistry
- May demonstrate hypercalciuria, hypocitraturia, or other biochemical abnormalities depending on the underlying cause.
Radiological Features
General Features
Nephrocalcinosis typically presents as increased echogenicity of the renal pyramids (medullary nephrocalcinosis) or the renal cortex (cortical nephrocalcinosis).
US
Renal ultrasound can show hyperechoic regions within the renal medulla or cortex. Ultrasound is a preferred first-line imaging modality due to its lack of radiation exposure.
CT
Non-contrast CT is highly sensitive and can show calcifications within the renal parenchyma.
XR
Plain abdominal radiographs may reveal diffuse, fine calcification in the renal area, particularly in advanced cases.
Grading and Staging
Nephrocalcinosis is generally graded based on the extent of calcification seen on imaging, with more severe disease associated with larger areas of calcification.
Differential Diagnosis
- Renal calculi: Both can present with calcifications within the kidney, but stones are usually located in the renal pelvis or calyces, while nephrocalcinosis involves the parenchyma.
- Medullary sponge kidney: This condition can cause medullary nephrocalcinosis but also presents with characteristic cystic dilatation of the collecting ducts.
Management
- Management of nephrocalcinosis involves treating the underlying condition, such as correcting metabolic abnormalities or stopping certain medications.
- Renal function is monitored regularly as nephrocalcinosis can lead to chronic kidney disease.
- For symptomatic stones, urology referral may be appropriate.