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Test ID: URAU Urea, 24 Hour, Urine

Reporting Name

Urea, 24 HR, U

Useful For

Assessment of protein intake and/or nitrogen balance

Specimen Type

Urine


Necessary Information


1. 24-Hour volume (in milliliters) is required.

2. For any timed collection the volume and length of collection is required.



Specimen Required


Supplies: Sarstedt 5 mL Aliquot Tube (T914)

Container/Tube: Plastic, urine tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect urine for 24 hours.

2. Mix well before taking aliquot.

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  30 days
  Ambient  7 days

Reference Values

≥18 years: 7-42 g/24 hours

Reference values have not been established for patients who are less than 18 years of age.

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

84540

LOINC Code Information

Test ID Test Order Name Order LOINC Value
URAU Urea, 24 HR, U 48999-7

 

Result ID Test Result Name Result LOINC Value
UREA Urea, 24 HR, U 48999-7
TM33 Collection Duration 13362-9
VL31 Urine Volume 3167-4
URECN Urea Concentration 63481-6

Clinical Information

Urea is a low molecular weight substance (60 Da) that is freely filtered by glomeruli, and the majority is excreted into the urine, although variable amounts are reabsorbed along the nephron. It is the major end product of protein metabolism in humans and other mammals. Approximately 50% of urinary solute excretion and 90% to 95% of total nitrogen excretion is composed of urea under normal conditions. Factors that tend to increase urea excretion include increases in glomerular filtration rate, increased dietary protein intake, protein catabolic conditions, and water diuretic states. Factors that reduce urea excretion include low protein intake and conditions that result in low urine output (eg, dehydration).

Interpretation

Because multiple factors (glomerular filtration rate, dietary protein intake, protein catabolic rate, hydration state, etc.) can independently affect the urinary excretion of urea, all of these factors must be taken into account when interpreting the results.

Clinical Reference

1. Lamb EJ, Jones GRD: Kidney function tests In: Rifai N, Horvath AR, Wittwer CT, eds. Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:498-500

2. Bankir L, Trinh-Trang- Tan MM: Urea and the kidney. In: Brenner BM eds. The Kidney. 6th ed. WB Saunders Company; 2000

Method Name

Kinetic Ultraviolet Assay

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.

Ambient

No

Refrigerate

OK

Frozen

OK

50% Acetic Acid

OK

Boric Acid

Preferred

Diazolidinyl Urea

OK

6M Hydrochloric Acid

OK

6M Nitric Acid

No

Sodium Carbonate

OK

Thymol

OK

Toluene

No

 

Forms

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

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day
Mayo Clinic Laboratories | Renal Diagnostics Catalog Additional Information:

mcl-kidney