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Urine Calcium (Ca), (Quantitative 24 hrs urine calcium)

March 22, 2021Lab TestsUrine Analysis

Sample

  1. 24 hours of urine is collected in the acid wash bottle.
    1. Add 10 to 20 mL of 6M/L HCl.
  2. 1 to 2 mL of a random urine sample can also be evaluated.
  3. Refrigerate the urine during collection.
  4. Or acidify the urine to pH <2.0 to dissolve the calcium salts.

Precautions

  1. Wash the bottle with dilute HCl and then rinse with water.
  2. Avoid contamination with calcium.
  3. Don’t use cork because it may contaminate the urine.
  4. If this test is done for metabolic disorder, then advise the patient to have a low calcium diet and stop calcium medications 1 to 3days before the urine collection.
  5. For patients with renal stones, the formation should have the same routine diet for the last three days before collecting the urine. Can continue medications.

Indications

  1. This is done to evaluate calcium intake (hypercalcemia).
  2. This also tells the rate of :
    1. Absorption of calcium from the GI tract.
    2. Bone Resorption.
    3. Renal loss.
  3. Measurement of calcium levels in urine and serum levels is used to diagnose and monitor calcium metabolism disorders.
  4. This test is also used in the stone evaluation and follow-up.
  5. Urine calcium is also advised for the calcium intake or rate of intestinal absorption, bone resorption, and renal loss.

Pathophysiology

  1. Calcium is the fifth most common element in the body.
    1. An average human body contains 1 kg of calcium.
Distribution of Calcium in the body

Distribution of Calcium in the body

  1. Calcium exists in three forms in the blood.
Distribution of Calcium in the body and metabolism

Distribution of Calcium in the body and metabolism

  1. Calcium in the body exists as intracellular and extracellular, and both have different functions.
Distribution of Calcium in the body

Distribution of Calcium in the body

  1. The parathyroid hormone maintains blood calcium levels.
Calcium metabolism

Calcium metabolism and control

  1. PTH indirectly increases the absorption of calcium from the gastrointestinal tract by producing the vit. D.
  2. PTH increases the serum calcium level by increasing bone resorption and mobilizing Calcium.
    1. Urine calcium is high in 30% to 80% of primary hyperparathyroidism cases, but it does not diagnostic.
Role of parathyroid in Calcium metabolism

Role of parathyroid in Calcium metabolism

  1. Calcium excretion:
    1. Mostly calcium is lost in the stool.
    2. A minimal amount is excreted in the urine.
    3. In hypercalcemia, there is increased secretion of calcium in the urine.
    4. In hypocalcemia, there is decreased secretion of calcium in the urine.
  2. Urinary calcium excretion is dependant upon the dietary intake of calcium.
  3. Increased urinary calcium takes place due to:
    1. Increased intestinal calcium absorption.
    2. The defect in the renal tubular reabsorption.
    3. Loss or reabsorption from the bone.
    4. Or a combination of the above possibilities.
  4. In primary hyperparathyroid disease, 30 to 80 % of the patient has high urinary calcium.
  5. Urine calcium does not have much value in the differential diagnosis.

NORMAL

Source 1

Diet mg/day mmol/Kg/day
Infants and child
up to 6.0 mg/Kg/day
0.15
Ca-free diet 5 to 40 0.13 to 1.0
Low to average Ca-diet 50 to 150 1.25 to 3.75
Average Ca-diet 100 to 300 2.50 to 7.50
  • The average Calcium diet is 800 mg/day.

Source 4

  • Normal diet = 100 to 300 mg/ 24 hours or 2.50  to 7.50 mmol/day.
  • Low calcium diet = 100 to 150 mg /24 hours or 1.25 to  3.75 mmol/day.

Another source

  • 50 to 250 mg/24 hours.

False raised values are seen in:

  1. Some of the drugs like calcitonin, vitamins A, K, and C.
  2. Corticosteroids.
  3. Urine is taken after meals with a high calcium intake, e.g, milk.
  4. Increased exposure to sunlight.
  5. Immobilization, especially in the children.

False decreased values are seen in:

  1. Increased ingestion of PO4, HCO3–, and antacid.
  2. Thiazide diuretics.
  3. Lithium therapy.
  4. Alkaline urine.
  5. Oral contraceptives and estrogens.

Increased urinary calcium:

  1. In hyperparathyroidism, 30 to 80% of the cases.
  2. Paget’s diseases.
  3. Renal diseases.
  4. Sarcoidosis.
  5. Breast cancer.
  6. Urinary bladder cancers.
  7. Multiple Myeloma.
  8. Bone metastasis (osteolytic).
  9. Vit.D intoxication.
  10. Thyrotoxicosis.
  11. Osteoporosis.
  12. Fanconi’s syndrome.
  13. Idiopathic hypercalciuria.
  14. Prolonged immobilization.

Decreased urinary calcium:

  1. Renal osteodystrophy.
  2. Rickets
  3. Hypoparathyroidism.
  4. Pre-eclampsia.
  5. Vit.D deficiency.
  6. Metastatic carcinoma of the prostate.
  7. Preeclampsia.
  8. Acute renal failure, nephritis, and nephrosis.
  9. Malabsorption conditions like :
    1. Celiac disease.
    2. Sprue disease.
    3. Steatorrhea.
  10. Drugs like Thiazide and oral contraceptives leads to decrease level.

    Normal urine picture:

    Physical features Chemical features Microscopic findings
    1. Color = Pale yellow or amber
    2. Appearance = Clear to slightly hazy
    3. pH = 4.5 to 8.0
    4. Specific gravity = 1.015 to 1.025
    1. Blood = Negative
    2. Glucose = Negative
    3. Ketones= Negative
    4. Protein = Negative
    5. Bilirubin = Negative
    6. Urobilinogen = Negative (±)
    7. Leucocyte esterase = Negative
    8. Nitrite for bacteria = Negative
    1. RBCs = Rare or Negative
    2. WBC = Rare or Negative
    3. Epithelial cells = Few
    4. Cast = Negative (Occasional hyaline)
    5. Crystal = Negative (Depends upon the pH of the urine)
    6. Bacteria = Negative

     


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