Hypercalciuria
also see
Hematuria
urinary calcium:urinary creatinine ratio >0.21, and 24-hour urinary calcium excretion of >4 mg/kg
Causes include:
idiopathic
hyperparathyroidism
immobilization
vitamin D intoxication
furosemide use
Renal U/S and KUB to r/o nephrocalcinosis or nephrolithiasis
The finding of hypercalciuria in a child who has hematuria should not exclude consideration of other etiologies of hematuria
Treat with increased fluid intake and possibly hydrochlorathiazide
Approximately 15% of children with idiopathic hypercalciuria will develop a renal stone within 5 years of diagnosis
Furosemide
therapy has been associated with the development of
hypercalciuria, most commonly among infants who receive the drug for
treatment of bronchopulmonary dysplasia. The first sign of
hypercalciuria is usually microscopic hematuria
with red blood cells (RBCs) in the urine.
Hypercalciuria usually is asymptomatic, but occasionally may be severe enough to
result in calcium stone formation and abdominal pain.
Any patient who is receiving chronic furosemide
or loop diuretic therapy, such as the infant described in the vignette, should
be screened routinely for RBCs
in the urine.
It is important to note that a urine
dipstick test that is positive for "blood" is not always indicative of RBCs
in the urine.
Urine may appear red or brown due to the
presence of hemoglobin, myoglobin, or porphyrins without
containing RBCs. The presence of RBCs discriminates between blood
originating from the urinary tract and other sources of discolored urine.
Therefore, a urine sample that is positive for "blood" on
dipstick must also contain RBCs to consider the diagnosis of hypercalciuria.
Screening the urine for calcium and creatinine
is the best initial step in diagnosing hypercalciuria.
A ratio of calcium to creatinine in a random urine sample of
greater than 0.25 is suggestive
of hypercalciuria, but it varies with age. Such a finding should be
followed by a 24-hour collection
of urine for calcium quantification. Urine calcium excretion greater than 4
mg/kg per day confirms the diagnosis.
Further evaluation should include measurement of serum calcium and
phosphate. If either of these values is abnormal, serum 25 hydroxyvitamin D,
1,25 dihydroxyvitamin D3, and parathyroid hormone levels also should be
measured. As with any child who has
persistent presence of RBCs
in the urine, renal
ultrasonography should be
obtained.
Although the infant in the vignette
developed hypercalciuria
due to
furosemide
therapy, idiopathic
hypercalciuria is more common.
Other causes of hypercalciuria include Bartter
syndrome, as a side effect of corticosteroid
therapy, sarcoidosis,
immobilization, vitamin D toxicity, and
distal renal tubular acidosis.
Treatment options for hypercalciuria depend on the etiology. Because
most cases are idiopathic, initial therapy involves aggressive hydration.
Inadequate reduction of urine calcium excretion may result in either nephrocalcinosis
or calcium stone formation.
In these patients,
hydrochlorothiazide therapy should be
instituted. Calcium oxalate stones are the most
common types of kidney stones in the United States.
CHLA Board Review 2005
Alon US, Berenbom A. Idiopathic hypercalciuria of childhood: 4- to
11-year outcome. Pediatr Nephrol. 2000;14:1011-1015
Coe FL, Parks JH, Moore ES. Familial idiopathic hypercalciuria. N Engl J
Med. 1979;300:337-340
Stapleton FB, Noe HN, Roy C III, Jerkins G. Hypercalciuria in children
with urolithiasis. Am J Dis Child. 1982;136:675-678