| Urea is a waste product, formed in
the liver and excreted in the urine at a relatively constant rate.
BUN (blood urea nitrogen) is a measurement of the nitrogen part of
urea, and is therefore an indirect measurement of the urea in the
bloodstream.
Elevations caused by:
- Kidney malfunction, as is seen in glomerulonephritis, pyelonephritis,
and shock.
- Increased metabolism of proteins, as is seen with GI bleeding, a
high protein meal, heart attack, diabetes, or infection.
- Dehydration and hemoconcentration
- Crush injuries
Decreases caused by:
- Liver failure
- Normal Pregnancy
- Excessive hydration
Note:
- BUN is a fast way to evaluate kidney function, but has some
limitations.
- Small changes in BUN may occur from medications, dietary changes and
hydration status and have little significance.
- Big changes in BUN occur only in fairly extreme circumstances.
- A more sensitive (but more complex) test of kidney function is the
creatinine clearance.
- With an elevated BUN, one way to distinguish between renal disease
and increased production of urea (such as is seen in GI bleeding) is
the BUN/creatinine ratio. It increases with increased metabolism, and
decreases with renal disease.
|
Normal Values:*
| |
mg/dL |
| Adults |
8-23 |
|
Children |
5-15 |
| Pregnancy |
5-12 |
*These are general values taken from a variety of
sources. The actual normal values may vary from lab to lab and from one
type of testing protocol to another.
|
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Operational Medicine 2001
Health Care in Military Settings
Bureau of Medicine and
Surgery
Department of the Navy
2300 E Street NW
Washington, D.C
20372-5300 |
Operational
Medicine
Health Care in Military Settings
CAPT Michael John Hughey, MC, USNR
NAVMED P-5139
January 1, 2001 |
United States Special Operations Command
7701 Tampa Point Blvd.
MacDill AFB, Florida
33621-5323 |
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