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HelpMayo Test ID URAU Urea, 24 Hour, 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.
Useful For
Assessment of protein intake and/or nitrogen balance
Special Instructions
Method Name
Kinetic Ultraviolet Assay
Reporting Name
Urea, 24 HR, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Frozen | 30 days | ||
| Ambient | 7 days |
Reject Due To
| All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. |
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).
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.
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.
Cautions
No significant cautionary statements
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 Description
Urea is hydrolyzed by urease to form ammonia and carbon dioxide. The ammonia formed then reacts with ketoglutarate and reduced nicotinamide adenine dinucleotide (NADH) in the presence of glutamate dehydrogenase to yield glutamate and NAD+. The decrease in absorbance is due to consumption of NADH and is measured kinetically at 340 nm.(Package insert: Roche Urea; BUN. Roche Diagnostics; V 8.0, 02/2020)
Specimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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 |
Day(s) Performed
Monday through Sunday