Hypercalciuria means excess calcium in the urine. It may be secondary—that is, a side-effect of some other condition causing high levels of calcium in the bloodstream—or it may be “idiopathic”—occurring on its own, with normal blood calcium levels.

Idiopathic hypercalciuria is a common disorder seen in 3% to 6% of children. While it may occur at any age, even in newborns, it is most often seen in children between 4 and 8 years old. Sometimes, it runs in families.

Excess calcium in the urine causes problems because it tends to form salts that crystallize. These crystals can cause pain or other urinary symptoms, depending upon their size and location. Large crystals are known as kidney stones.

Causes / Risk Factors for Hypercalciuria

The digestive system, bones, kidneys and hormones (endocrine system) can all affect calcium levels in the urine, so there are many possible causes. In many cases, the direct cause is unknown.

Although not common in children, hyperparathyroidism is a condition where hormones released from the parathyroid glands can cause hypercalciuria.

Risk factors for hypercalciuria include:

• Family history of kidney stones
• Not drinking enough fluids
• Diet high in sodium and protein
• Taking medicines such as furosemide (Lasix), corticosteroids, excessive vitamin D, and methylxanthines, such as theophylline

Associated Problems / Conditions

Children with hypercalciuria are at increased risk of developing:

• Kidney stones
• Blood in the urine
• Urinary symptoms such as burning, or needing to go often or urgently
• Abdominal pain
• Repeated urinary tract infections (UTI)
• Weakened bones (osteoporosis) from loss of calcium

Signs and Symptoms of Hypercalciuria

Children with any of the following may have hypercalciuria:

• Blood in urine, either seen with your eyes or under a microscope
• Pain with urination, needing to go urgently or frequently, or bedwetting
• Side, belly, or lower belly pain
• Kidney stones
• Repeated urinary tract infections (UTI)
• Irritability (seen in infants)

These signs and symptoms may occur at any age but are often first seen in 4- to 8-year-olds.

How is Hypercalciuria Diagnosed?

Hypercalciuria is mainly diagnosed by measuring calcium in the urine using the following tests:

• 24-hour urine test for calcium and other minerals (if the child’s age makes this impossible, a single urine sample is tested)
• Blood tests to rule out certain diseases that may cause hypercalciuria
• Genetic testing, especially if there is a family history of kidney stones
• Imaging studies, especially renal ultrasound, which does not deliver any radiation, to look for kidney abnormalities or stones (we are part of the Image Gently alliance).

How is Hypercalciuria Treated?

Our treatment for hypercalciuria includes:

• Addressing any secondary disease causing the hypercalciuria.
• Making changes to the diet with the help of a registered dietitian. Changes will include increasing the amount of fluids the child drinks every day and lowering the sodium in their diet. However, to promote healthy bones and growth, we do not generally recommend restricting dietary calcium or protein.
• If diet changes aren’t enough, the doctor may need to add medicines to decrease calcium in the urine or prevent stone formation.
• Repeating 24-hour urine tests to check how well treatment is working.
• Hyperparathyroidism requires a referral to our Endocrinology team for treatment.

Prognosis / Long-term Outlook

Most often, with dietary changes—and medicine if needed—you can lower urine calcium into the normal range, lowering the risk of kidney stones. Because idiopathic hypercalciuria is an inborn tendency, these children will always need to watch their diet to decrease the risk of developing kidney stones and other associated problems.