What is Nephrocalcinosis?
Nephrocalcinosis is a medical term first introduced in 1934 by Fuller Albright. It refers to an increased amount of calcium in the kidney, which can take the form of calcium oxalate or calcium phosphate. Some suggest that the term should only refer to deposits of calcium phosphate and that the term ‘oxalosis’ should be used for calcium oxalate deposits.
This condition is characterized by calcium deposits in the kidney tissue and tubes. It might be discovered on an x-ray in people with normal kidney function, or it could cause sudden or gradual kidney damage. There are many factors that can lead to the development of this condition, and its overall impact on kidney health depends on the root cause.
What Causes Nephrocalcinosis?
Nephrocalcinosis is a condition where calcium generally deposits throughout the kidney. This doesn’t include isolated calcium deposits associated with specific kidney injuries. Nephrocalcinosis can result from conditions that lead to high levels of calcium, phosphate or oxalate in the blood or urine.
The formation of calcium phosphate crystals, which is connected to this condition, happens when the urine’s pH is alkaline. Several diseases have been linked to this process, and they all work through similar underlying mechanisms.
Certain conditions can cause both high calcium levels in the blood (hypercalcemia) and high calcium levels in the urine (hypercalciuria). These include primary hyperparathyroidism, vitamin D therapy, sarcoidosis (an inflammatory disease), Milk-alkali syndrome, and congenital hypothyroidism (a condition present from birth where the thyroid gland doesn’t produce enough thyroid hormone).
There are also conditions that trigger high calcium levels in the urine (hypercalciuria) without causing high calcium in the blood (hypercalcemia). Some of these are distal renal tubular acidosis, medullary sponge kidney, inherited disorders affecting the kidneys, and chronic low levels of potassium in the blood (chronic hypokalemia).
Certain conditions can cause both high phosphate levels in the blood (hyperphosphatemia) and urine (hyperphosphaturia). Examples of these include tumor lysis syndrome (a rapid release of cells into the blood caused by certain types of cancer treatment), and oral sodium phosphate preparations used for bowel cleansing.
Finally, there are conditions that can trigger high phosphate levels in the urine (hyperphosphaturia) without causing high phosphate levels in the blood (hyperphosphatemia). Inherited disorders affecting the kidneys are a common cause, as well as various genetic disorders like Dent disease, Lowe syndrome, and different forms of hypophosphatemic rickets.
Risk Factors and Frequency for Nephrocalcinosis
Primary hyperparathyroidism, sarcoidosis, hypervitaminosis D, distal renal tubular acidosis, medullary sponge kidney, loop diuretic abuse, and certain hereditary disorders can all lead to a condition called nephrocalcinosis, which is essentially an accumulation of calcium in the kidneys. Here’s how each of these causes works:
- In primary hyperparathyroidism, kidney stones and nephrocalcinosis are common issues. Despite the parathyroid hormone pushing for the reabsorption of calcium in the body, the high amount of calcium filters into the urine instead.
- Sarcoidosis can lead to heightened levels of calcium in the blood and urine. In instances where it affects the kidneys, up to 50% of those cases can result in nephrocalcinosis.
- Excessive vitamin D consumption can increase the absorption of calcium in the intestine, which in turn leads to more calcium and phosphate in the urine and possibility of nephrocalcinosis. Children with nephropathic cystinosis, a kidney condition, are particularly susceptible.
- Distal renal tubular acidosis, a condition where there are high levels of calcium in the urine but not in the blood, is a major cause of nephrocalcinosis. This condition can also lead to hypocitraturia, another condition promoting calcium buildup.
- Medullary sponge kidney is a disorder that dilates the papillary collecting ducts, leading to common occurrences of stones and nephrocalcinosis.
- High doses of loop diuretics, drugs that lower fluid levels in the body, can also risk nephrocalcinosis.
- Lastly, genetic disorders such as X-linked hypercalciuric nephrolithiasis, X-linked hypophosphatemic rickets, and others can lead to nephrocalcinosis as well.
Signs and Symptoms of Nephrocalcinosis
Nephrocalcinosis is generally a silent, long-lasting disease that is usually found during an abdomen scan. This scan might be done because of the discomfort from the presence of kidney stones, which is common in this condition. These stones are due to chronic high levels of calcium in blood and urine, leading to renal colic, which is a type of severe abdominal pain. Frequently, the disease can also cause excessive urination and extreme thirst due to chronic high blood calcium levels, changes in the medulla of kidney, or in Bartter syndrome.
It is also possible for Nephrocalcinosis to appear suddenly along with kidney failure in certain situations such as tumor lysis syndrome and acute phosphate nephropathy.
Testing for Nephrocalcinosis
If a radiology test confirms that you have nephrocalcinosis, which is a condition where calcium deposits form in your kidneys, your doctor will want to determine what’s causing it. They might run blood tests to measure the levels of electrolytes, calcium, and phosphate in your blood. They may also check the pH level in your urine to see if you’re experiencing distal renal tubular acidosis, a condition that prevents your kidneys from properly removing acids from your blood.
In addition to these tests, your doctor might ask you to collect your urine over a 24-hour period on two different days. They will use these samples to measure how much calcium, phosphate, oxalate, citrate, and creatinine your body is removing from your blood.
Treatment Options for Nephrocalcinosis
The treatment for nephrocalcinosis, which is a condition where calcium deposits form in your kidneys, is primarily focused on addressing the root cause. This often involves implementing strategies to reduce the levels of calcium, phosphate, or oxalate in the urine. One common approach is to increase your fluid intake to produce at least 2 liters of urine each day, which helps to flush out these substances.
For patients with hypercalciuria, a condition characterized by excess calcium in the urine, specific dietary measures can be helpful. These include reducing the amount of animal protein you consume, limiting your sodium intake, and increasing your potassium intake. Some patients may also benefit from a type of water pill known as a thiazide diuretic, which can help lower the amount of calcium in the urine. It should be noted, though, that this medication isn’t suitable for everyone – specifically, patients with high levels of calcium in their blood shouldn’t use it.
In cases where nephrocalcinosis is caused by a condition called distal renal tubular acidosis, potassium citrate can be used in patients with a low level of urinary citrate and a pH less than 7. This helps to replace lost potassium and bring the urinary citrate level back to normal, which in turn increases the ability of calcium to dissolve, rather than forming deposits.
What else can Nephrocalcinosis be?
Nephrocalcinosis, or the accumulation of calcium in the kidneys, usually stems from dystrophic calcification. This term refers to a phenomenon where calcification occurs due to tissue damage, rather than the buildup of excessive urinary components. This condition can result from several issues, including:
- Infarction: a situation where the blood supply to a tissue or organ is blocked
- Malignancy: the presence of cancerous cells
- Infection: when harmful bacteria or viruses invade the body
What to expect with Nephrocalcinosis
Nephrocalcinosis is a medical condition where calcium deposits form in the kidneys. Certain specific causes like Dent disease, primary hyperoxaluria, and hypomagnesemic hypercalciuric nephrocalcinosis, can lead to serious kidney problems if not treated well. These problems can include chronic renal failure, a condition where the kidneys stop functioning over time, or even End Stage Renal Disease, where the kidneys have almost or completely stop working. Once nephrocalcinosis is found through radiological methods, like an X-ray, it’s usually not reversible, meaning it can’t usually be cured or eliminated.
Possible Complications When Diagnosed with Nephrocalcinosis
If X-linked hypophosphatemic rickets isn’t treated properly, it can result in hindered bone growth. In the hypomagnesemia-hypercalciuria syndrome, children might experience symptoms like violent muscle contractions and spasms, muscle cramps, and fatigue. Some patients may also experience loss of hearing and vision issues.
Common Symptoms:
- Stunted bone growth (in case of untreated X-linked hypophosphatemic rickets)
- Violent muscle contractions and spasms
- Muscle cramps
- Fatigue or weakness
- Loss of hearing (in some patients)
- Vision issues (in some patients)
Preventing Nephrocalcinosis
Patients diagnosed with nephrocalcinosis, a condition where calcium builds up in the kidneys, should drink plenty of water each day. The aim is to produce at least 2 liters of urine a day. This helps to flush out the excess calcium from the kidneys. Additionally, patients should also pay attention to their diet. If they are passing high levels of calcium in the urine, also known as hypercalciuria, they should limit the amount of protein they eat. They should also aim to consume under 100 milliequivalents of sodium daily. This simply means eating a diet low in salt.
