Pediatric Hypercalciuria Treatment & Management

The goals of therapy in children with hypercalciuria should be the elimination of symptoms, prevention of renal stone formation, and preservation of kidney function.

Dietary modification is a mandatory part of effective therapy. The child should be referred to a dietitian to accurately assess daily calcium, animal protein, and sodium intake. As previously mentioned, a trial of a low-calcium diet can be done transiently to determine if exogenous calcium intake is contributing to the high urinary calcium. However, great caution should be used when trying to restrict calcium intake for long periods.

Because of the concern regarding poor bone matrix calcification and subsequent osteoporosis, no child should receive less than the daily recommended intake (DRI) of calcium for long periods without careful monitoring. If the dietary calcium is restricted to less than the DRI, bone density measurements and growth parameters should be taken at regular intervals to monitor the development of osteoporosis and growth retardation. Reducing sodium and animal protein to the DRI may facilitate lowering of urinary calcium. However, the authors recommend that great caution be used when placing any child on a diet with less than the DRI of calcium and that a dietitian be consulted for assistance. If this does not provide the desired results of symptom relief, prevention of nephrolithiasis, and normalization of calcium excretion (< 4 mg/kg/d), pharmacotherapy should be initiated.

Another indication for starting medication is evidence of bone demineralization or history of previous renal stone formation despite a low calcium diet. Hydrochlorothiazide (HCTZ) and other thiazide-type diuretics are the agents most frequently used to treat hypercalciuria. These agents are discussed further in the Medication section.

Lithotripsy may be needed to remove a urinary stone that is not spontaneously passed and is associated with urinary obstruction.

Reduction of dietary calcium lowers urinary calcium but may increase urinary oxylate. The new calcium-oxylate product may result in supersaturation.

Surgical care is not usually necessary in children with hypercalciuria unless an underlying urological abnormality is present that predisposes a child to develop renal stones. Rarely, sonographic techniques are insufficient to remove a renal stone, and surgery is needed to relieve an obstruction.

A pediatric nephrologist should evaluate and treat any child with proven or suspected hypercalciuria. Once hypercalciuria is diagnosed, a pediatric dietitian should be consulted to help construct an appropriate diet. In cases where urological abnormalities are detected or renal stones form without prompt spontaneous passage, a pediatric urologist should be involved in caring for the child.

Dietary modifications are important components in treating children with hypercalciuria. General guidelines that are applicable to most children with hypercalciuria include the following:

• Maintain water intake at 1500 mL/m²/d.
• Restrict dietary calcium to the DRI for age. The US Food and Drug Administration (FDA) sets the DRI (or recommended daily allowance [RDA]) by doubling the estimated daily need. This was done to ensure an adequate amount of calcium (and other vitamins and minerals) intake for growth and development.
• Some people believe that this is an overestimation of the amount of calcium intake actually needed. In otherwise healthy children with normal urinary calcium excretion, the excess calcium is removed in the urine without consequence. However, in children who have hypercalciuria, this amount of dietary calcium may induce symptoms or renal stone formation.
• Consequently, some health care providers believe it may be safe to use less than the DRI of calcium in children who are still having hypercalciuria and renal stone formation with normal amounts of calcium in their diet. If such a diet is used, monitoring bone mineralization and growth parameters at regular intervals is essential. Alternatively, if the desired urinary calcium excretion is not achieved with the RDI of calcium, pharmacotherapy can be initiated.
• Restricting dietary sodium may also be helpful in children with hypercalciuria. As mentioned above, a direct relationship between sodium chloride intake and urinary calcium excretion is observed. Therefore, limiting salt intake should help reduce the amount of urinary calcium. No data indicate that high salt intake alone can induce the clinical syndrome of hypercalciuria. However, evidence may show that lower sodium diets help reduce urinary calcium excretion in children who have idiopathic hypercalciuria. A good target range for dietary sodium intake is 2-3 mEq/kg/d.
• In children with a history of calcium oxalate stones, lowering dietary oxalate is indicated.
• Diets high in animal protein may produce a larger metabolic acid load in adults and contribute to stone formation. Studies in children are not available; however, protein intakes higher than the DRI are not necessary and may be harmful.

No limitations of activity are needed, but an effort should be made to ensure adequate fluid intake with increased insensible losses (eg, exercise).