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Urine Urea Nitrogen
Test CodeCPT Codes
84540
Includes
Preferred Specimen
Random or Timed Urine Specimen
Minimum Volume
Instructions
Collect random specimen in a sterile urine cup or collect timed specimen in a 24-hour urine jug. A 2-hour timed collection is the preferred specimen. For timed specimens: Record start and stop time or number of hours collected on jug. If transferring specimen from larger jug to a smaller cup, measure volume first and record on smaller cup, along with the start and stop time or number of hours.
This test is for Urea Nitrogen measurement on Urine. For Urea Nitrogen Clearance, order URCLEAR, which also requires blood draw. For Urea Nitrogen measurement on Plasma or Serum only, order BUN. For Urea Nitrogen measurement on Body Fluids, order MISUN.
Transport Container
24-hour urine container or sterile urine cup
Transport Temperature
Specimen Stability
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Methodology
Colorimetric
Setup Schedule
Monday - Sunday, 8:00 am - 3:00 pm upon receipt
Report Available
Reference Range
Urine Volume: 800 - 1800 mL/24 hours
Urine Urea Nitrogen/Total Volume Ratio: 12 - 20 g/24 hour
Clinical Significance
Urea Clearance measures the amount of urea that is cleared from plasma by the kidneys in one minute.
Urea is a low molecular weight substance (Mol. Wt.=60) 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 which tend to increase urea excretion include increases in glomerular filtration rate, increased dietary protein intake, protein catabolic conditions, and water diuretic states. Factors which reduce urea excretion include low protein intake and conditions which result in low urine output (eg, dehydration).
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 by taken into account when interpreting the results.
This test is for Urea Nitrogen measurement on Urine. For Urea Nitrogen Clearance, order URCLEAR, which also requires blood draw. For Urea Nitrogen measurement on Plasma or Serum only, order BUN. For Urea Nitrogen measurement on Body Fluids, order MISUN.