Calcium, Urine

Calcium, Urine

Synonym/acronym: N/A.

Common use

To indicate sufficiency of dietary calcium intake and rate of absorption. Urine calcium levels are also used to assess bone resorption, renal stones, and renal loss of calcium.

Specimen

Urine (5 mL) from an unpreserved random or timed specimen collected in a clean plastic collection container.

Normal findings

(Method: Spectrophotometry)
AgeConventional Units*SI Units (Conventional Units × 0.025)*
Infant and childUp to 6 mg/kg per 24 hrUp to 0.15 mmol/kg per 24 hr
Adult on average diet100–300 mg/24 hr2.5–7.5 mmol/24 hr
*Values depend on diet.

Description

Regulating electrolyte balance is a major function of the kidneys. In normally functioning kidneys, urine levels increase when serum levels are high and decrease when serum levels are low to maintain homeostasis. Analyzing urinary electrolyte levels can provide important clues to the functioning of the kidneys and other major organs. Tests for calcium in urine usually involve timed urine collections during a 12- or 24-hr period. Measurement of random specimens may also be requested. Urinary calcium excretion may also be expressed as calcium-to-creatinine ratio: In a healthy individual with constant muscle mass, the ratio is less than 0.14.

This procedure is contraindicated for

    N/A

Indications

  • Assist in establishing the presence of kidney stones
  • Evaluate bone disease
  • Evaluate dietary intake and absorption
  • Evaluate renal loss
  • Monitor patients on calcium replacement

Potential diagnosis

Increased in

  • Acromegaly (related to imbalance in vitamin D metabolism)
  • Diabetes (related to increased loss from damaged kidneys)
  • Fanconi’s syndrome (evidenced by hereditary or acquired disorder of the renal tubules that results in excessive calcium loss)
  • Glucocorticoid excess (related to action of glucocorticoids, which is to decrease the gastrointestinal absorption of calcium and increase urinary excretion)
  • Hepatolenticular degeneration (Wilson’s disease) (related to excessive electrolyte loss due to renal damage)
  • Hyperparathyroidism (related to increased levels of PTH which result in increased calcium levels)
  • Hyperthyroidism (related to increased bone turnover; excess circulating calcium is excreted by the kidneys)
  • Idiopathic hypercalciuria
  • Immobilization (related to disruption in calcium homeostasis and bone loss)
  • Kidney stones (evidenced by excessive urinary calcium; contributes to the formation of kidney stones)
  • Leukemia and lymphoma (some instances)
  • Myeloma (calcium is released from damaged bone; excess circulating calcium is excreted by the kidneys)
  • Neoplasm of the breast or bladder (some cancers secrete PTH or PTH-related peptide that increases calcium levels)
  • Osteitis deformans (calcium is released from damaged bone; excess circulating calcium is excreted by the kidneys)
  • Osteolytic bone metastases (carcinoma, sarcoma) (calcium is released from damaged bone; excess circulating calcium is excreted by the kidneys)
  • Osteoporosis (calcium is released from damaged bone; excess circulating calcium is excreted by the kidneys)
  • Paget’s disease (calcium is released from damaged bone; excess circulating calcium is excreted by the kidneys)
  • Renal tubular acidosis (metabolic acidosis resulting in loss of calcium by the kidneys)
  • Sarcoidosis (macrophages in the granulomas interfere with vitamin D regulation by converting it to its active form; vitamin D increases circulating calcium levels, and excess is excreted by the kidneys)
  • Schistosomiasis
  • Thyrotoxicosis (increased bone turnover; excess circulating calcium is excreted by the kidneys)
  • Vitamin D intoxication (increases calcium metabolism; excess is excreted by the kidneys)

Decreased in

    Hypocalcemia (other than renal disease) Hypocalciuric hypercalcemia (familial, nonfamilial) Hypoparathyroidism (PTH instigates release of calcium; if PTH levels are low, calcium levels will be decreased) Hypothyroidism Malabsorption (celiac disease, tropical sprue) (related to insufficient levels of calcium) Malignant bone neoplasm Nephrosis and acute nephritis (related to decreased synthesis of vitamin D) Osteoblastic metastases Osteomalacia (related to vitamin D deficiency) Pre-eclampsia Pseudohypoparathyroidism Renal osteodystrophy Rickets (related to deficiency in vitamin D) Vitamin D deficiency (deficiency in vitamin D results in decreased calcium levels)

Critical findings

    N/A

Interfering factors

  • Drugs that can increase urine calcium levels include acetazolamide, ammonium chloride, asparaginase, calcitonin, corticosteroids, corticotropin, dexamethasone, dihydroxycholecalciferol, diuretics (initially), ergocalciferol, ethacrynic acid, glucocorticoids, mannitol (initially), meralluride, mercaptomerin, mersalyl, metolazone, nandrolone, parathyroid extract, parathyroid hormone, plicamycin, prednisolone, sodium sulfate, sulfates, torsemide, triamcinolone, triamterene, viomycin, and vitamin D.
  • Drugs that can decrease urine calcium levels include angiotensin, bicarbonate, calcitonin, cellulose phosphate, citrates, diuretics (chronic), lithium, mestranol, methyclothiazide, neomycin, oral contraceptives, parathyroid extract, polythiazide, sodium phytate, spironolactone, thiazides, trichlormethiazide, and vitamin K.
  • Failure to collect all the urine and store the specimen properly during the 24-hr test period invalidates the results.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating the effectiveness of the body’s absorption of calcium.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s endocrine, genitourinary, and musculoskeletal systems and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Provide a nonmetallic urinal, bedpan, or toilet-mounted collection device. Address concerns about pain and explain that there should be no discomfort during the procedure.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Usually a 24-hr time frame for urine collection is ordered. Inform the patient that all urine must be saved during that 24-hr period. Instruct the patient not to void directly into the laboratory collection container. Instruct the patient to avoid defecating in the collection device and to keep toilet tissue out of the collection device to prevent contamination of the specimen. Place a sign in the bathroom to remind the patient to save all urine.
  • Instruct the patient to void all urine into the collection device and then to pour the urine into the laboratory collection container. Alternatively, the specimen can be left in the collection device for a health care staff member to add to the laboratory collection container.
  • Note that there are no fluid or medication restrictions unless by medical direction.
  • Instruct the patient to follow a normal calcium diet for at least 4 days before test. Protocols may vary among facilities.

Intratest

  • Potential complications: N/A
  • Ensure that the patient has complied with dietary restrictions; ensure that a normal calcium diet has been followed for at least 4 days prior to the procedure.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection.
  • Random Specimen (collect in early morning)

  • Obtain urine specimen in a properly labeled plastic collection container and immediately transport urine. If an indwelling catheter is in place, it may be necessary to clamp off the catheter for 15 to 30 min before specimen collection. Cleanse specimen port with antiseptic swab, and then aspirate 5 mL of urine with a 21- to 25-gauge needle and syringe. Transfer urine to a plastic container.
  • Timed Specimen

  • Obtain a clean 3-L urine specimen container, toilet-mounted collection device, and plastic bag (for transport of the specimen container). The specimen must be refrigerated or kept on ice throughout the collection period. If an indwelling urinary catheter is in place, the drainage bag must be kept on ice.
  • Begin the test between 6 and 8 a.m. if possible. Collect first voiding and discard. Record the time the specimen was discarded as the beginning of the timed collection period. The next morning, ask the patient to void at the same time the collection was started, and add this last voiding to the container. Urinary output should be recorded throughout the collection time.
  • If an indwelling catheter is in place, replace the tubing and container system at the start of the collection time. Keep the container system on ice during the collection period or empty the urine into a larger container periodically during the collection period; monitor to ensure continued drainage, and conclude the test the next morning at the same hour the collection began.
  • At the conclusion of the test, compare the quantity of urine with the urinary output record for the collection; if the specimen contains less than the recorded output, some urine may have been discarded, invalidating the test.
  • Include on the collection container’s label the amount of urine collected and test start and stop times. Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be sent to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Instruct the patient to resume usual diet as directed by the HCP.
  • Nutritional Considerations: Increased urine calcium levels may be associated with kidney stones. Educate the patient, if appropriate, as to the importance of drinking a sufficient amount of water when kidney stones are suspected.
  • Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include ACTH, albumin, aldosterone, ALP, biopsy bone marrow, BMD, bone scan, calcitonin, calcium ionized, calculus kidney stone analysis, catecholamines, chloride, collagen cross-linked telopeptides, CBC, CT pelvis, CT spine, cortisol, CK and isoenzymes, DHEA, fecal fat, glucose, HVA, magnesium, metanephrines, osteocalcin, oxalate, PTH, phosphorus, potassium, protein total, radiography bone, renin, sodium, thyroid scan, thyroxine, US thyroid and parathyroid, UA, uric acid, and vitamin D.
  • Refer to the Endocrine, Genitourinary, and Musculoskeletal systems tables at the end of the book for related tests by body system.
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