nephrocalcinosis

see also:

• renal colic
• urolithiasis / renal stones / renal calculi

• Medullary nephrocalcinosis is a condition characterized by the deposition of calcium salts in the renal medulla and is usually detected by the finding of renal medullary hyperechogenicity on USS or CT scans.

• Medullary Sponge Kidney (MSK)
  • MSK is characterized by cystic dilatation of the renal tubules leading to medullary hyperechogenicity. Ultrasound patterns can vary and are correlated with disease severity and prognosis
• Distal Renal Tubular Acidosis:
  • This condition can present with intense echoes throughout the renal pyramids due to the associated metabolic disturbances
• Vitamin D Toxicity:
  • Overdose of vitamin D can lead to increased calcium levels, resulting in an intense echogenic rim around the pyramids
• Tubulopathies:
  • Various types of tubulopathies can cause slight hyperechogenicity around the sides and tip of the medullary pyramids
• Nephrocalcinosis

• primary hyperparathyroidism
• primary renal tubular acidosis
• sarcoidosis
• milk-alkali syndrome
• primary hyperoxaluria
• idiopathic hypercalcuria
• idiopathic

• medullary sponge kidney (calcified collecting ducts)
• renal malignancies
• cyst
• haematoma
• papillary necrosis
• tuberculosis (TB)
• hydatid cyst

• chronic glomerulonephritis (GN)
• old cortical necrosis

The causes of medullary nephrocalcinosis can be multifactorial and include a variety of systemic and renal-specific conditions:

• Metabolic Disorders: Conditions such as hyperparathyroidism can lead to hypercalcaemia, resulting in calcium deposition in the renal medulla.
• Renal Tubular Acidosis (RTA): Distal RTA, for example, is characterized by the kidney's inability to acidify urine properly, leading to metabolic acidosis, hypokalemia, and calcium deposition in the kidneys.
• Inherited Conditions: Certain genetic disorders can predispose individuals to nephrocalcinosis.
• Medications: Some drugs can increase the risk of nephrocalcinosis by affecting calcium metabolism or renal function.
• Infections: Chronic urinary tract infections, especially with urease-producing organisms, can lead to the formation of struvite stones and secondary nephrocalcinosis.
• Obstructive Uropathy: Chronic obstruction of the urinary tract can lead to stasis and secondary stone formation.
• gout: Although primarily affecting joints, gout can sometimes be associated with renal manifestations, including nephrocalcinosis.
• Autoimmune Diseases: Conditions like Sjögren's syndrome (SS) can involve the kidneys and lead to nephrocalcinosis.

### Clinical Evaluation

- History and Physical Examination: A thorough history to identify any underlying conditions or risk factors such as recurrent urinary tract infections, metabolic disorders, or a family history of kidney stones or renal diseases. Physical examination may help in identifying signs related to potential underlying causes.

### Laboratory Tests

- Blood Tests: To assess renal function (creatinine, urea), electrolytes (to detect abnormalities such as hypercalcemia or hypokalemia), and acid-base status (bicarbonate levels). These tests can help in identifying conditions like hyperparathyroidism or renal tubular acidosis. - Urinalysis: To check for pH, presence of crystals, and signs of infection. An alkaline urine pH may suggest distal renal tubular acidosis, while the presence of crystals could indicate a metabolic disorder. - Specific Tests: Depending on the suspected underlying cause, additional tests may include parathyroid hormone levels (for hyperparathyroidism), autoimmune markers (for diseases like Sjögren’s syndrome), and genetic testing in familial cases.

### Imaging Studies

- Ultrasound: The first-line imaging modality for diagnosing nephrocalcinosis. It can reveal hyperechogenicity in the medulla, which is indicative of calcium deposition[1]. - CT Scan: Provides detailed imaging and can help in assessing the extent of calcification. It is particularly useful in cases where ultrasound findings are inconclusive or when there is a need to rule out other renal pathologies.

### Differential Diagnosis

The work-up should also aim to differentiate medullary nephrocalcinosis from other causes of renal medullary hyperechogenicity and to identify any associated conditions such as gouty arthritis or systemic diseases affecting the kidneys.

### Management

The management of medullary nephrocalcinosis focuses on treating the underlying cause, if identified, and preventing further calcium deposition. This may involve dietary modifications, hydration, medications to correct metabolic abnormalities, and in some cases, addressing any obstructive uropathy.