Nephrocalcinosis - Types, Causes, Symptoms, Diagnosis and Treatment

Introduction:

Nephrocalcinosis is characterized by excessive calcium deposition into the parenchyma of the kidneys and tubules. It may cause severe or chronic kidney damage. The nephrocalcinosis can be accidentally diagnosed by radiographic examination in a well-functioning kidney. Many different conditions play a role as the underlying cause of nephrocalcinosis, and this underlying condition determines the prognosis (outcome) after treatment. In contrast, many patients with nephrocalcinosis may not progress to end-stage kidney disease. However, if the underlying cause is not treated, it may result in progressive kidney failure.

What Is Nephrocalcinosis?

Nephrocalcinosis is a kidney disorder in which excessive calcium is deposited in the kidneys. It is common in premature babies and can also occur in adults. In most cases of nephrocalcinosis, both the kidneys are affected.

How Serious Is Nephrocalcinosis?

Nephrocalcinosis is not a life-threatening condition, and it usually does not cause symptoms in most cases and does not progress to end-stage severe kidney disease. However, if the underlying cause is left untreated, it can cause kidney failure in the long run.

What Are the Types of Nephrocalcinosis?

Nephrocalcinosis is classified based on the radiographic demonstration and calcifications of the kidneys' parenchyma (functional tissue of an organ composed of a group of similar cells).

According to the radiographic appearance, nephrocalcinosis can be:

• Microscopic Nephrocalcinosis: In this type, the crystalline forms of calcium (calcium oxalate or calcium phosphate) are precipitated all over and can only be seen under a microscope.

• Macroscopic Nephrocalcinosis: Larger areas of calcifications are seen, which are visible to the naked eye on the radiograph.

• Chemical Nephrocalcinosis: This type shows increased levels of calcium deposition in kidney cells, especially in the tubular epithelium, causing kidney function impairment.

According to its association with renal calculi it can also be categorized as:

• Medullary Nephrocalcinosis: The most common form is characterized by the particular involvement of the medullary pyramids of the kidney.

• Cortical Nephrocalcinosis: This type is rare, covering the entire kidney parenchyma. It is commonly associated with severe metabolic disorders, such as primary hyperoxaluria or end-stage renal disease.

What Causes Nephrocalcinosis?

Nephrocalcinosis can be caused by various factors, which include underlying causes or conditions, medications or supplements, and infections. In addition, some inherited conditions can also cause nephrocalcinosis.

Some of the inherited conditions that cause nephrocalcinosis are :

• Type 1 endocrine neoplasia.

• Distal renal tubular acidosis

• Chronic granulomatous disease.

• Primary hyperoxaluria.

• Bartter syndrome.

• Alport syndrome.

• Primary hyperaldosteronism.

• Liddle syndrome.

• Deficiency of 11 - beta-hydroxylase.

• Williams syndrome.

• Beta-thalassemia.

Some of the other causes include:

• Primary hyperparathyroidism.

• Distal renal tubular acidosis (RTA).

• Hypervitaminosis-D state (high levels of vitamin D).

• Hypercalcemia (excessive calcium levels).

• Sarcoidosis.

• Phosphate supplementation.

• Medullary sponge kidney.

• Underlying osteoporosis.

• Premature birth.

• Certain medications like Acetazolamide.

• Kidney diseases and AIDS-related diseases.

What Are the Causes of Nephrocalcinosis in Preterm Babies and Infants?

Newborn babies are at greater risk of nephrocalcinosis due to renal tubular insufficiency as nephrogenesis is not completed until thirty-four to thirty-six weeks of gestation. In addition, due to still-developing kidneys with continuous cell proliferation within the renal tubules, there is a high chance of crystal formation and aggregation, causing nephrocalcinosis.

What Are the Symptoms of Nephrocalcinosis?

In most cases, nephrocalcinosis may not cause any symptoms, but the symptoms can be caused due to the underlying disease condition. However, in addition, individuals may suffer from the symptoms that are caused due to kidney problems which can be :

• Fever and chills.

• Blood in the urine.

• Nausea and vomiting.

• Abdominal pain.

• Pain in sides and back, groin region, or near testicles.

How Is Nephrocalcinosis Diagnosed?

The diagnostic investigation of nephrocalcinosis is done by :

1. Blood Tests:

• Thyroid hormone tests.

• Serum electrolytes test.

• Serum albumin, calcium, and potassium test.

2. Urine Analysis:

• Microscopic examination and culture of urine for diagnosing any urinary tract infection.

• 24-hour test urinary levels of calcium oxalate, potassium, magnesium, uric acid and citrates.

3. Radiographic Investigation:

• Abdominal X-rays for detection of urinary stones and nephrocalcinosis.

• Ultrasound.

• CT scan for diagnosing and differentiating the medullary and cortical calcifications.

4. Endoscopy:

• The procedure followed for distinguishing between nephrolithiasis and nephrocalcinosis require direct visual examination through endoscopy.

5. Renal Biopsy:

• A procedure in which a piece of tissue or cells of an organ is collected and tested in the laboratory. This procedure is followed to assess the underlying cause.

How Is Nephrocalcinosis Treated?

The treatment for nephrocalcinosis is carried out by treating the underlying cause. The treatment relies upon reducing the symptoms and preventing calcium deposition.

• In treating conditions like hypercalcemia and hypercalcemic nephropathy in which excessive calcium levels are present in the blood, adequate hydration is provided through salines (isotonic sodium chloride solution) to prevent damage to the kidney.

• In the case of macroscopic nephrocalcinosis, Thiazide Diuretics (the medication which helps to release more sodium into the urine) are prescribed, and dietary restriction of salt intake is advised.

• Potassium and magnesium supplements are given.

• Potassium citrate supplementation is recommended in cases of idiopathic (unknown cause) hypercalciuria and distal tubular renal acidosis (RTA) because the potassium citrate acts as a chelating agent (a chemical agent that reacts with metal ions of substance and forms a water-soluble stable component) that for urinary calcium and thus reduces stone formation.

• In Type I hyperoxaluria, large doses of Pyridoxine are given to reduce oxalate production.

• Parathyroidectomy in case of the hyperfunctioning thyroid gland is done.

• Surgical intervention in case of renal stones causing obstruction and infection.

What Are the Dietary Modifications to Be Followed for Nephrocalcinosis?

• In order to make at least two liters of urine excretion daily, more fluid intake is recommended.

• Restriction of high protein animal food.

• Restriction of sodium intake.

What Are the Complications of Nephrocalcinosis?

If the underlying conditions of nephrocalcinosis are left untreated, it might lead to the complications like:

• Chronic kidney failure.

• Renal colic.

• Renal tubular dysfunction.

• Renal infections.

Conclusion:

Although nephrocalcinosis is not a life-threatening condition, early detection and management of the underlying cause are essential to avoid long-term kidney failure, and if one already has severe kidney disease, nephrocalcinosis can be irreversible in some cases. So it is necessary to diagnose and treat as early as possible.