Nephrocalcinosis

Definition: Deposits of calcium (in the form of calcium phosphate and calcium oxalate) in the kidney, a process that may result in reduced kidney function.

Nephrocalcinosis can be caused by several conditions including: the excess excretion of calcium by the kidney, renal tubular acidosis, medullary sponge kidney, hypercalcemia (high calcium levels in the blood), renal cortical necrosis, and tuberculosis.

Nephrocalcinosis is relatively common in premature infants, partly from intrinsic kidney calcium losses and partly from enhanced calcium excretion when they are given diuretics. It is of special concern to Bartter patients because a high percentage of these patients have nephrocalcinosis. Anyone diagnosed with Bartters Syndrome should have an Xray, Ultrasound or Cat Scan to determine if nephrocalcinosis is present.

The underlying condition causing nephrocalcinosis needs to be treated, otherwise continued damage can lead to eventual kidney failure.

Causes, incidence, and risk factors

Nephrocalcinosis may be caused by a number of conditions:

  • Bartter Syndrome
  • Excess excretion of calcium by the kidney
  • Renal tubular acidosis
  • Medullary sponge kidney
  • Hypercalcemia (high calcium levels in the blood)
  • Renal cortical necrosis
  • Tuberculosis

Fragments of calcium oxalate or calcium phosphate may break free from the kidney and provide nuclei for formation of stones (nephrolithiasis). This may result in obstructive uropathy, possibly leading to eventual kidney failure if the obstructing stones are not passed in the urine or removed. Nephrocalcinosis may therefore be discovered when symptoms of renal insufficiency/renal failure, obstructive uropathy, or urinary tract stones develop. This condition is relatively common in premature infants, partly from intrinsic kidney calcium losses and partly from enhanced calcium excretion when they are given loop diuretics.

Symptoms

There are generally no early symptoms. Later symptoms related to nephrocalcinosis and associated disorders may include the following:

  • Increased urine volume or urine output, decreased
  • Urinary hesitancy (difficulty initiating the flow of urine)
  • Dribbling of urinary incontinence
  • Decrease in the force of the urinary stream, stream small and weak
  • Increased urinary frequency or urgency
  • A need to urinate at night (nocturia)
  • Painful urination (burning or stinging with urination)
  • Feeling of incomplete emptying of the bladder
  • Blood in the urine
  • Flank pain or back pain
    • one or both sides
    • progressive
    • severe
    • spasm-like (colicky)
    • may radiate or move to lower in flank, pelvis, groin, genitals
  • Nausea, vomiting
  • Generalized swelling, fluid retention
  • Decrease in sensation, especially the hands or feet
  • Changes in mental status
    • drowsy, lethargic, hard to arouse
    • delirium or confusion
    • coma
  • Seizures
  • Blood in the vomit or stools
  • Easy bruising or bleeding

Signs and tests

An examination but may indicate disorders that occur as a consequence of nephrocalcinosis. There may be signs of fluid overload, such as abnormal heart and lung sounds, if kidney function is poor.

  • An abdominal film shows renal calcification.
  • An abdominal CT scan shows nephrocalcinosis.

Other tests may be performed to diagnose and determine the extent of associated disorders.

Treatment

The goal of treatment is reduction of symptoms. The cause of the disorder must be treated. If the cause is type 1 renal tubular acidosis, vitamin D and calcium should not be given to correct bone disorders associated with the condition because this will worsen nephrocalcinosis.

Medications that enhance calcium excretion should be discontinued. Never discontinue any medications without consulting your health care provider.

Conditions that result from the disorder should be treated in their usual manner.

The following medications may be helpful in preventing nephrocalcinosis.1

  • ACE Inhibitor: A type of high blood pressure medicine which may decrease urinary citrate. ACE stands for Angiotension Converting Enzyme. This type of medication blocks the activity of an enzyme which would otherwise create chemicals in the body that would increase the blood pressure.
  • Aluminum Hydroxide: This is occasionally used in patients with Struvite or infection stones to help bind intestinal phosphate and limit its absorption. It’s also used as a substitute oxalate binding agent where calcium is not appropriate.
  • Aluminum Hydroxide: Tends to cause constipation. Cannot be used in patients with kidney failure because of possibly dangerous accumulations in the body.
  • Amiloride: A type of potassium sparing “water pill” or diuretic.
  • Beelith: A magnesium supplement.
  • Bucillamine: Experimental drug that increases dissolvability of cystine. Expected to be more effective with fewer side effects than penicillamine.
  • Calcitriol: Another name for activated Vitamin D or Vitamin D3.
  • Calcitonin: Hormone that increases calcium deposition in bone and is generally the exact opposite of parathyroid hormone.
  • Calcium Citrate: The preferred type of calcium supplement for kidney stone formers. The extra citrate helps avoid any increase in calcium stone formation.
  • Captopril: A blood pressure medicine which is thought to be able to bind with cystine and make it more dissolvable. While safe and well tolerated, its effectiveness in cystine stone disease is unclear.
  • Cellulose: A strong binder of calcium in the digestive tract.
  • Cholestyramine: A strong binding agent for oxalate in the intestinal tract. Takes the place of calcium in enteric hyperoxaluria. Effective, but tends to have side effects.
  • Codeine: An oral pain medication of medium strength. An opioid.
  • Demerol: A strong Opioid type of pain medication.
  • Diamox: Normally used for glaucoma, this (Acetazolamide) medication will block excretion of acid from the kidneys and alkalinize the urine. Can be of use in severe cystinuria, but generally should be avoided in most stone patients if possible.
  • Dilantin: A medicine commonly used for seizures. Can interfere with Vitamin D activity.
  • Diuretic: A type of medication that causes the kidneys to make more urine. Can be used to increase urinary volume but only as a last resort. Some diuretics, like thiazide, can be used to help decrease stone disease while others cannot. Originally intended as therapy for blood pressure and heart failure.
  • Diuril: A common thiazide medication.
  • Dyazide: A high blood pressure medication composed of a thiazide and triamterene. Should not be used in stone patients because triamterene can sometimes form kidney stones by itself!
  • Elmiron: Originally designed as a therapy for (Pentosan Polysulfate) interstitial cystitis, an unusual inflammatory condition of the urinary bladder. This medication restores the normal mucus coating of the bladder lining. There is evidence that Elmiron can be a strong inhibitor of calcium oxalate stone formation, but only limited human studies are available at this time. Still, it could be of some use in the most severe and intractable cases of high urinary oxalate.
  • Estrogen: A female hormone. Will increase calcium in bone.
  • Fosamax: A new class of medication that is designed for osteoporosis. Works almost as good as estrogen in replacing calcium in bone.
  • Hydrochlorothiazide: The standard thiazide medication. Usually not the preferred agent in stone disease because it must be taken twice a day while other thiazides like Naqua and Lozol only need to be taken once daily.
  • Lozol (Indapamide): A long acting water pill (diuretic) that has an almost identical function to thiazide but is not technically one of them. Will also take calcium out of the urine and return it to the bloodstream. Only needs to be taken once a day.
  • Magnesium Oxide: Common magnesium supplements. (Beelith) and Magnesium Hydroxide
  • Moduretic: Combination of thiazide and amiloride. The amiloride returns potassium to the blood that would otherwise be lost. Needs to be taken twice a day. A good substitute for Dyazide.
  • Naqua: A long acting thiazide. Only needs (trichlormethiazide) to be taken once a day.
  • Opioid: A group of medicines chemically related to extracts from opium. Morphine and Codeine are examples.
  • Orthophosphate: An oral form of phosphate supplement.
  • Oxythiozolidine: (OZT) An experimental medication that decreases liver production of oxalate by about one third.
  • Percocet and Percodan: Oral tablets of a moderately strong Opioid medication.
  • Penicillamine: A binding agent for cystinuria. Side effects are severe and common. Only about 50 percent of patients with cystinuria can tolerate this medication even though it is very effective.
  • Persantine: Can somewhat reduce the excessive loss of phosphate in Renal Phosphate Leak.
  • Prednisone: The most common oral steroid. A very effective anti-inflammatory, but has several side effects.
  • Pyridoxine: Another name for Vitamin B-6. Steroids A group of medications with similar chemical compositions that resemble natural anti-inflammatory agents in the body. They have many side effects including fluid retention and increasing urinary calcium. Talwin A moderately strong pain medicine. Not an opioid.
  • Thiazides: The name for a group of medicines that are chemically similar. They are “water pills” in that they force the kidneys to produce more urine. They are unique because they can take excess calcium in the urine and return it to the bloodstream. This is particularly beneficial in older women with high urinary calcium levels and osteoporosis.
  • Triamterene: A potassium sparing diuretic. (Dyrenium) Should not be used in kidney stone patients because it forms stones.
  • UroPhos-K: Experimental form of slow release orthophosphate. Avoids most of the side effects of orthophosphate supplements and is quite effective in calcium stone disease.
  • Vitamin D: The vitamin that controls intestinal absorption of calcium and phosphate from the digestive tract. Needs to be converted to its most active form, Vitamin D3, by the kidney to work. Vitamin D3 is also called calcitriol.

Expectations (prognosis)

The outcome varies depending on the extent of complications and the cause of the disorder.

Complications

  • Acute renal failure
  • Chronic renal failure
  • Kidney stones
  • Obstructive uropathy (acute or chronic, unilateral or bilateral)

Calling your health care provider Call your health care provider if symptoms indicate that disorders associated with nephrocalcinosis may be present.

Emergency symptoms include suddenly decreased urine output, and decreased consciousness related to calcium levels and/or kidney failure.

Prevention

Prompt treatment of causative disorders, including renal tubular acidosis, may help prevent nephrocalcinosis.

References

1. UrologyStone.com
2. Medline Plus

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