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Test Code OXU Oxalate, 24 Hour, Urine

Reporting Name

Oxalate, 24 Hr, U

Useful For

Monitoring therapy for kidney stones using 24-hour urine collections

 

Identifying increased urinary oxalate as a risk factor for stone formation

 

Diagnosis of primary or secondary hyperoxaluria

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Urine


Necessary Information


24-hour volume (in milliliters) is required.



Specimen Required


Patient Preparation: For 24 hours before, as well as during the collection process, patient should not take large doses (>2 g orally/24 hours) of vitamin C.

Supplies:

-Diazolidinyl Urea (Germall) 5.0 mL (T822)

-Sarstedt Aliquot Tube, 5mL (T914)

Container/Tube: Plastic tube or a clean, plastic aliquot container with no metal cap or glued insert

Specimen Volume: 4 mL

Collection Instructions:

1. Add 5 mL of diazolidinyl urea (Germall) as a preservative at start of collection or refrigerate specimen during and after collection.

2. Collect urine for 24 hours.

3. Mix container thoroughly and aliquot urine into plastic vial.

4. Specimen pH should be between 4.5 and 8 and will stay in this range if kept refrigerated. Specimens with pH above 8 indicate bacterial contamination, and testing will be canceled. Do not attempt to adjust pH, as it will adversely affect results.

Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens 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

0.11-0.46 mmol/24 h

9.7-40.5 mg/24 h

The reference value is for a 24-hour collection. Specimens collected for other than a 24-hour period are reported in unit of mmol/L for which reference values are not established.

 

Reference values have not been established for patients who are younger than 16 years.

Day(s) Performed

Monday through Saturday

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. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

83945

Clinical Information

Oxalate is an end product of glyoxalate and glycerate metabolism. Humans do not have an enzyme capable of degrading oxalate, therefore it must be eliminated by the kidney.

 

In tubular fluid, oxalate can combine with calcium to form calcium oxalate stones. In addition, high concentrations of oxalate may be toxic to kidney cells.

 

Increased urinary oxalate excretion results from inherited enzyme deficiencies (primary hyperoxaluria), gastrointestinal disorders associated with fat malabsorption (secondary hyperoxaluria), or increased oral intake of oxalate-rich foods or vitamin C (ascorbic acid).

 

Since increased urinary oxalate excretion promotes calcium oxalate stone formation, various strategies are employed to lower oxalate excretion.

Report Available

3 to 5 days

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Method Name

Enzymatic

Forms

If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Disease States

  • Hyperoxaluria