What investigations should be done for suspected nephrocalcinosis?

From the Guidelines

Investigations for suspected nephrocalcinosis should include a renal ultrasound as the initial imaging study, followed by laboratory tests such as comprehensive blood tests and urinalysis to confirm the diagnosis and identify the underlying cause. The most recent and highest quality study, 1, published in 2023, recommends performing kidney ultrasound at least yearly in patients who have not yet reached stage 5D CKD to assess the presence of stones and nephrocalcinosis.

Imaging Studies

• Renal ultrasound is the preferred initial imaging study due to its high sensitivity in detecting calcium deposits in the kidneys.
• Non-contrast CT scan may be used for further clarification if needed, but with caution to avoid irradiating examinations as much as possible and using low-dose scans if required, as suggested by 1.

Laboratory Tests

• Comprehensive blood tests should include measurements of serum calcium, phosphate, parathyroid hormone (PTH), vitamin D levels, creatinine, and electrolytes to assess kidney function and identify metabolic abnormalities.
• Urinalysis and 24-hour urine collection are essential to evaluate for hypercalciuria, hyperoxaluria, hypocitraturia, and abnormal urinary pH, as recommended by 1 and 1.
• Additional specialized tests may include genetic testing for hereditary conditions like distal renal tubular acidosis or primary hyperoxaluria, particularly in patients with family history or early-onset disease, as suggested by 1 and 1.

Importance of Early Diagnosis and Targeted Treatment

Early diagnosis and targeted treatment can help prevent progressive kidney damage and preserve renal function. The specific etiology of nephrocalcinosis is crucial for appropriate management, as treatment varies significantly depending on whether the cause is hyperparathyroidism, renal tubular acidosis, medullary sponge kidney, or other conditions.

Key Considerations

• The clinical practice recommendations from 1 and 1 emphasize the importance of regular follow-up and monitoring of patients with suspected nephrocalcinosis.
• The choice of investigations and treatments should be guided by the most recent and highest quality evidence, with consideration of the individual patient's needs and circumstances.

From the Research

Investigations for Nephrocalcinosis

To diagnose and manage nephrocalcinosis, several investigations can be performed, including:

• Complete urinalysis, including urinary calcium excretion, urine pH, and electrolytes 2
• Arterial blood gas (ABG) and serum electrolytes (sodium, potassium, calcium, magnesium, and phosphorus) 2
• Renal function tests 2, 3
• Parathyroid and gonadotropin-sex hormone assay 2
• Radiological evaluation, such as:
  • Ultrasonography (US) 4, 5
  • Computed tomography (CT) 4, 5
  • Kidney/ureter/bladder (KUB) X-ray 4
• Genetic testing, such as DNA extraction and sequencing to analyze the CLDN16 gene 2
• Biochemical parameters, including serum creatinine, phosphate, calcium, intact parathyroid hormone (iPTH), 25-hydroxy vitamin D, and albumin 3

Diagnostic Imaging

Diagnostic imaging plays a crucial role in the diagnosis of nephrocalcinosis. The choice of imaging modality depends on the clinical presentation and the suspected underlying cause.

• CT combined with either US or KUB is recommended for confirming the diagnosis of nephrocalcinosis 4
• Ultrasound examination alone may be sufficient in some cases, especially in children 5
• Plain abdominal films or non-enhanced computed tomography may be necessary in some cases 5

Metabolic Evaluation

Metabolic evaluation is essential in the diagnosis and management of nephrocalcinosis, especially in children.

• Metabolic disorders, such as primary hyperoxalurias, should be ruled out 5
• Biochemical parameters, including serum creatinine, phosphate, calcium, iPTH, and 25-hydroxy vitamin D, should be evaluated 3