Home
HelpTest ID: CALU Calcium, 24 Hour, Urine
Reporting Name
Calcium, 24 Hr, UUseful For
Evaluation of calcium oxalate and calcium phosphate kidney stone risk, and calculation of urinary supersaturations
Evaluation of bone diseases, including osteoporosis and osteomalacia
Clinical Information
Calcium is the fifth most common element in the body. It is a fundamental element necessary to form electrical gradients across membranes, an essential cofactor for many enzymes, and the main constituent in bone. Under normal physiologic conditions, the concentration of calcium in serum and in cells is tightly controlled. Calcium is excreted in both urine and feces. Ordinarily about 20% to 25% of dietary calcium is absorbed and 98% of filtered calcium is reabsorbed in the kidney. Traffic of calcium between the gastrointestinal tract, bone, and kidney is tightly controlled by a complex regulatory system that includes vitamin D and parathyroid hormone. Sufficient bioavailable calcium is essential for bone health. Excessive excretion of calcium in the urine is a common contributor to kidney stone risk.
Interpretation
Increased urinary calcium excretion (hypercalciuria) is a known contributor to kidney stone disease and osteoporosis. Many cases are genetic (often termed "idiopathic"). Previously such patients were often divided into fasting versus absorptive hypercalciuria depending on the level of urine calcium in a fasting versus fed state, but the clinical utility of this approach is now in question. Overall, the risk of stone disease appears increased when 24-hour urine calcium is >250 mg in men and >200 mg in women. Thiazide diuretics are often used to reduce urinary calcium excretion, and repeat urine collections can be performed to monitor the effectiveness of therapy.
Known secondary causes of hypercalciuria include hyperparathyroidism, Paget disease, prolonged immobilization, vitamin D intoxication, and diseases that destroy bone (such as metastatic cancer or multiple myeloma).
Urine calcium excretion can be used to gauge the adequacy of calcium and vitamin D supplementation, for example in states of gastrointestinal fat malabsorption that are associated with decreased bone mineralization (osteomalacia).
Special Instructions
Analytic Time
Same day/1 dayDay(s) and Time(s) Performed
Monday through Sunday; Continuously
Clinical Reference
1. Curhan GC, Willett WC, Speizer FE, Stampfer MJ: Twenty-four-hour urine chemistries and the risk of kidney stones among women and men. Kidney Int 2001;59:2290-2298
2. Metz MP: Determining urinary calcium/creatinine cut-offs for the pediatric population using published data. Ann Clin Biochem 2006;43:398-401
3. Pak CY, Britton F, Peterson R, et al: Ambulatory evaluation of nephrolithiasis. Classification, clinical presentation and diagnostic criteria. Am J Med 1980;69:19-30
4. Pak CY, Kaplan R, Bone H, et al: A simple test for the diagnosis of absorptive, resorptive and renal hypercalciurias. N Engl J Med 1975;292:497-500
Method Name
Photometric, NM-BAPTA Reaction
Specimen Type
UrineSpecimen Required
Collection Container/Tube: 24-hour graduated urine container with no metal cap or glued insert
Submission Container/Tube: Plastic, 5-mL tube (T465) or a clean, plastic aliquot container with no metal cap or glued insert
Specimen Volume: 4 mL
Collection Instructions:
1. Collect urine for 24 hours.
2. Refrigerate specimen within 4 hours of completion of 24-hour collection.
Additional Information:
1. 24-Hour volume is required.
2. See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens in Special Instructions for multiple collections.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Frozen | 14 days | ||
| Ambient | 72 hours |
Reference Values
Males: <250 mg/24 hours
Females: <200 mg/24 hours
Reference values have not been established for patients <18 years and >83 years of age.
Reference values apply to 24-hour collection.
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
82340
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CALU | Calcium, 24 Hr, U | 6874-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CA24 | Calcium, 24 Hr, U | 6874-2 |
| TM114 | Collection Duration | 13362-9 |
| VL110 | Urine Volume | 3167-4 |
| CACN | Calcium Concentration | 18488-7 |
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
mml-bone-minerals