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Nephrocalcinosis

Practice Essentials

Nephrocalcinosis is a condition in which calcium levels in the kidneys are increased. Most often, the increase in renal calcium is generalized, as opposed to the localized increase observed in calcified renal infarct and caseating granulomas of renal tuberculosis. See the image below.

Axial CT scans from patient with long history of r

Axial CT scans from patient with long history of renal tubular acidosis. Images show bilateral medullary nephrocalcinosis (early arterial phase).

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Signs and symptoms

Presentation is primarily determined by the underlying etiology, though in many cases the condition remains asymptomatic and is identified only as a radiologic abnormality. The physical findings are nonspecific and reflect the underlying disorders responsible.

Clinical features of hypercalcemic nephropathy may include the following:

Relative vasopressin resistance with decreased renal concentrating ability and increased free water diuresis, manifesting as polyuria and polydipsia

Renal glycosuria, reduced glucose tubular maximum, aminoaciduria, and nonglomerular proteinuria

Reversible hypertension

Kidney failure, usually reversible but sometimes not

Clinical features of microscopic nephrocalcinosis (on the basis of animal studies) may include the following:

Reduced concentration capacity

Increased blood urea nitrogen (BUN)

Prolongation of nephron transit time in the distal tubule

Acute pyelonephritis or calculous ureteral obstruction with kidney failure

Clinical features of macroscopic nephrocalcinosis (the form most commonly seen) may include the following:

Renal colic

Hematuria

Passage of urinary stones

Urinary tract infection

Polyuria and polydipsia

Hypertension

Proteinuria

In Dent disease, loss of low-molecular-weight proteins, hypercalciuria, and nephrolithiasis

Microscopic pyuria

Distal tubular dysfunction with a mild salt-losing defect

Proximal tubular dysfunction (unusual)

Secondary distal tubular acidosis

Kidney failure

See Presentation for more detail.

Diagnosis

Laboratory studies that may be useful include the following:

Serum calcium, phosphate, and albumin levels

Blood urea nitrogen (BUN) and serum creatinine levels

Estimated glomerular filtration rate (eGFR)

Serum potassium concentration

Urinalysis and urine culture

Assessment of 24-hour urinary excretion of calcium, oxalate, citrate, and uric acid

Urinary magnesium levels

Parathyroid hormone and thyroid-stimulating hormone levels

Imaging studies that may be considered include the following:

Radiography (eg, kidney-ureter-bladder [KUB])

Ultrasonography (more sensitive than conventional radiography)

Computed tomography (CT; more effective in detecting calcification)

Magnetic resonance imaging (MRI) offers no advantages over these modalities and is not warranted unless another compelling indication is present.

See Workup for more detail.

Management

Pharmacologic and other nonsurgical treatments for hypercalcemia and hypercalcemic nephropathy include the following:

Adequate hydration with an isotonic sodium chloride solution (the single most effective measure for reversing hypercalcemia and protecting the kidneys)

Cinacalcet (for correction of hyperparathyroidism)

Chemotherapeutic agents (for osteolytic malignancies)

Steroids (to decrease intestinal calcium absorption and vitamin-D activity)

Hydroxychloroquine (for sarcoid granulomas)

Calcitonin or bisphosphonates (to inhibit bone resorption)

Pharmacologic and other nonsurgical treatments for macroscopic nephrocalcinosis include the following:

Thiazide diuretics (eg, hydrochlorothiazide)

Dietary salt restriction

Potassium and magnesium supplementation

Citrate supplementation (preferably as potassium citrate)

High-dose pyridoxine

Surgery options that may be considered for urinary stones causing obstruction include the following:

Percutaneous nephrolithotomy

Laser and
shock wave lithotripsy

Stent placement

Open surgery (rarely necessary)

Parathyroidectomy may be considered for removal of enlarged adenomas.

See Treatment and Medication for more detail.

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