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Blood biochemistry: urea
Synonym(s): Blood urea nitrogen, BUN
Overview
- Produced in liver from ammonia derived from tissue/dietary protein and excreted by kidneys.
- Important marker of kidney function, protein metabolism and upper gastrointestinal tract hemorrhage.
Uses
In combination
- Renal disease.
- Liver disease.
- Upper gastrointestinal tract hemorrhage.
Sampling
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Tests
Methodologies
- Typically measured as (total) blood urea nitrogen (BUN) (based on nitrogen portion of urea).
- Blood urea is based on the entire molecule of urea.
- Blood strips can be used to get a rapid results. Do not give precise reading but will show if levels are significantly elevated.
Availability
- Widely available.
Validity
Sensitivity
- Low sensitivity in detection of renal dysfunction. Renal mass must be reduced by approximately 75% before BUN values are consistently outside of reference interval.
Specificity
- Low specificity for detection of renal dysfunction.
Technique intrinsic limitations
- Only significant in conjunction with other laboratory and clinical findings.
Most useful to assess in conjunction with a urine specific gravity Urinalysis: specific gravity.
Result Data
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Further Reading
Publications
Refereed papers
- Recent references from VetMedResource and PubMed.
Other sources of information
- Ettinger S J & Feldman E C (2000) Eds. Textbook of Veterinary Internal Medicine. 5th edn. W B Saunders & Co, USA.
- Kaneko J J, Harvey J W & Brass M L (1997) Eds. Clinical Biochemistry of Domestic Animals. 5th edn. Academic Press, USA.
- Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa University Press, USA.