Calcium, Urine

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Category:

Turnaround Time: Within 1 day
CPT Code:

82340

Test Type: 25 mL aliquot Urine (24-hour)
Stability Time:

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Overview:

Reflects intake, rates of intestinal calcium absorption, bone resorption and renal loss. Those processes relate to parathyroid hormone and vitamin D levels. Evaluation of bone disease, calcium metabolism, renal stones (nephrolithiasis);1 idiopathic hypercalciuria,2 and especially, parathyroid disorders. Follow-up of patients on calcium therapy for osteopenia.

High in 30% to 80% of instances of primary hyperparathyroidism, but urinary calcium excretion does not consistently, reliably distinguish hyperparathyroidism from other entities. High in sarcoidosis.3 Increased with immobilization, with steroid therapy, with Paget disease, and in primary (idiopathic) hypercalciuria.4 Increased with entities causing high ultrafiltrable calcium: ectopic hyperparathyroidism, some cases of renal tubular acidosis, Fanconi syndrome, increased calcium intake, vitamin D intoxication, hyperthyroidism, diabetes mellitus, acromegaly, glucocorticoid excess, some cases of Crohn's disease and ulcerative colitis, myeloma, some instances of leukemia and lymphoma, and carcinoma metastatic to bone. Reported relationship to hematuria in children.5

Low in familial hypocalciuric hypercalcemia, for which urine calcium measurements are mandatory; low with thiazide diuretics, vitamin D deficiency, renal osteodystrophy, vitamin D resistant rickets, hypoparathyroidism, pseudohypoparathyroidism and preëclampsia.6

Decreased in patients on oral contraceptives. Lacks specificity for hyperparathyroidism when increased. Five percent of the population have hypercalciuria.4

Twenty percent to 25% patients who form calcium stones have hyperuricosuria. Urinary calcium reflects in part the relation between GFR and tubular reabsorption.

1. Silverberg SJ, Shane E, Jacobs TP, et al. Nephrolithiasis and bone involvement in primary hyperparathyroidism. Am J Med. 1990 Sep; 89(3):327-334. PubMed 2393037

2. Lemann J Jr, Gray RW. Idiopathic hypercalciuria. J Urol. 1989; 141(3 Pt 2):715-718. PubMed 2645429

3. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 50-1981. A 76-year-old woman with intermittent hypercalcemia. N Engl J Med. 1981 Dec 10; 305(24):1457-1464. PubMed 7300865

4. Erickson SB. Hypercalciuria. Mayo Clin Proc. 1981; 56:579.

5. Stark H, Tieder M, Eisenstein B, Davidovits M, Litwin A. Hypercalciuria as a cause of persistent or recurrent haematuria. Arch Dis Child. 1988 Mar; 63(3):312-313. PubMed 3355215

6. Taufield PA, Ales KL, Resnick LM, Druzin ML, Gertner JM, Laragh JH. Hypocalciuria in preeclampsia. N Engl J Med. 1987Mar 19; 316(12):715-718. PubMed 3821810

Collection Details:

Patient Preparation:

Urinary calcium results are more meaningful if the patient has been on a low calcium, neutral ash diet for three days prior to urine collection. Drugs affecting mineral metabolism should be withdrawn, if possible, two to four weeks prior to and during collection. These include antacids, phosphates, diuretics, glucocorticoids, carbonic anhydrase inhibitors, and anticonvulsants.

Collection Instructions:

The test request form must state date and time collection started and date and time collection finished. State total volume.

Preferred: Plastic urine container with at least 10 mL 6N HCl (hydrochloric acid). Specimens submitted without preservatives should be acidified after receipt to a pH <2.0 to dissolve calcium salts.

Instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Transport the specimen promptly to the laboratory. Container must be labeled with patient's full name, room number, date and time collection started, and date and time collection finished. pH must be <2.

Maintain specimen at room temperature.