What is Nephrocalcinosis?
Nephrocalcinosis is caused by deposition of calcium salts in the renal parenchyma which is due to hyperparathyroidism.
It is once known as Albright's calcinosis after FullerAlbright (American endocrinologist) who made a huge contribution to it.
The term nephrocalcinosis points to a situation where both calcium oxalate and calcium phosphate are deposited in kidneys. It can cause severe kidney injury inflicting heavy pain.
This situation can arise due to multiple different conditions and can cause continuous determined progressive kidney dysfunction.
This situation can eventually come together combine to form a solid mass. In the beginning stages, nephrocalcinosis can be diagnosed on an x-ray, which looks like a fine granular mottling over the kidney renal outlines.
It is very commonly identified as an incidental finding with medullary sponge kidney on an abdominal x-ray.
It may become critical enough to cause renal tubular acidosis (accumulation of acid due to failure of kidneys) or even end-stage renal failure (gradual loss of kidney function) which is due to deposited calcium in renal tissue. Nephrocalcinosis can also arise due to renal tubular acidosis.
Symptoms of Nephrocalcinosis
Usually, this condition doesn’t show any symptoms, but if symptoms are seen they are mostly related to the causative process, Blood in the urine, fever, and chills, vomiting and nausea, severe pain in the belly area, back pain, groin or testicles.
These include renal colic, polyuria, and polydipsia
- Renal colic is normally caused by already existing nephrolithiasis, which may occur in patients with chronic hypercalciuria.
- The above-mentioned diseases from reduced urinary concentrating capacity as can be seen in hypercalcemia, medullary nephrocalcinosis of any cause, or in children with Bartter syndrome.
Nephrocalcinosis can be caused by multiple reasons as stated above and present only with renal/kidney failure. The causes also include tumor lysis syndrome and occasional cases of enteric hyperoxaluria.
Causes of Nephrocalcinosis
Nephrocalcinosis is always linked with symptoms that cause hypercalcemia, hyperphosphatemia, and the higher excretion of calcium, phosphate, and/or oxalate in the urine passage.
Urine with high pH levels can be due to Nephrocalcinosis but only if it is seen along with hypercalciuria and hypocitraturia.
This is because having normal urinary citrate usually avoids the formation of calcium crystals. Along with Nephrocalcinosis, hypercalcemia and hypercalciuria cases, the following can occur:
- Nephrocalcinosis is one of the most common symptoms.
- Vitamin D therapy can cause nephrocalcinosis, as it increases the absorption of calcium in the body instead of passing it over urine and causing bone resorption, resulting in hypercalcemia and hypercalciuria.
- Medullary sponge kidney
- Renal tubular acidosis
- Renal tuberculosis
- Renal papillary necrosis
Hypercalciuria without hypercalcemia
Below conditions can cause nephrocalcinosis in along with hypercalciuria without hypercalcemia:
- Distal renal tubular acidosis
- Medullary sponge kidney
- Neonatal nephrocalcinosis and loop diuretics
- Inherited tubulopathies
- Chronic hypokalemia
Patients normally suffer from both of the diseases, however, cases are seen where one occurs without the other disease.
When the concentration of the reactants increases beyond the limit, calcium oxalate and calcium phosphate crystals are formed.
The calcium oxalate and calcium phosphate crystal deposits are formed in the inner medullary interstitum which is at the basement membranes of the thin limbs of the loop of Henle which is part of the nephron.
Over time, calcium phosphate can result in plaques which can enlarge into nearby interstitial tissue & it can even rupture into the tubule lumen which further increases the risk of calcium oxalate stone formation.
Diagnosis of Nephrocalcinosis
Imaging techniques are used in diagnoses for the most part of nephrocalcinosis. Ultrasound (US), abdominal plain film and CT imaging are the common three techniques used for diagnoses of nephrocalcinosis.
If at least two expert radiologists make their diagnosis on ultrasound (US), abdominal plain film and CT imaging, then nephrocalcinosis considered to be present.
In certain cases, a renal biopsy is conducted in addition if the above-mentioned imaging techniques are not good enough to confirm nephrocalcinosis.
Additional tests are needed to find the underlying root cause once radiologists confirm the disease. These tests are needed because the underlying condition may require different treatment based on reasons which are not dependent on nephrocalcinosis.
These additional tests are used to measure electrolytes, serum, phosphate and calcium, and the urine pH. If no underlying issue can be found, then the test has to be done once again & measurements of the excretion of calcium, phosphate, oxalate, citrate, and creatinine are looked at.
Treatment of Nephrocalcinosis
Generally, a high intake of fluids to result in urine output of higher than 2 liters a day can be very helpful for all of the patients who are suffering from nephrocalcinosis.
Patients suffering from hypercalciuria need to reduce their calcium excretion by limiting animal protein, and also limiting sodium intake to less than 100 meg a day and also need to gradually reduce potassium intake.
Changing one’s diet should help with the reduction of hypercalciuria. If not, then a thiazide diuretic can be provided to patients who do not have hypercalcemia.
Citrate should not be given to those patients who already have high urine pH values which are equal to or greater than 7.
Prognosis of Nephrocalcinosis
The underlying cause determines the prognosis of nephrocalcinosis normally. However, most of the cases of nephrocalcinosis do not reach the end and final stage of renal disease.
If it is not treated properly, it can become severe and lead to renal dysfunction. This includes primary hyperoxaluria (excessive urine excretion of oxalate), hypomagnesemia hypercalciuric nephrocalcinosis (high levels of calcium in the urine) and Dent's disease (excess calcium in urine resulting in renal stones).
Once a patient is diagnosed with nephrocalcinosis disease, it is very unlikely to be treated completely. However, it is possible to treat is partial, as reported in patients who have completed their treatment of hypercalciuria and hyperoxaluria successfully along with following corrective intestinal surgery to treat the damage caused by disease.