Urea In Serum

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Contents 1 Reference-interval 2 Principle 3 Clinical-significance 4 Increases 5 Specimen 6 More General Terms 7 Additional Terms 8 References

Reference-interval

• Male & Female: 6 - 18 mg/dL

Principle

• see urea in body fluid

Clinical-significance

• Urea, formed in the liver by the deamination of amino acids, is the primary method of nitrogen excretion. Urea, then, is the end product of protein metabolism & is formed in the liver. After synthesis, urea travels through the blood & is excreted in the urine.
  
• Acute or chronic renal failure is the most common cause of high BUN levels. In prerenal failure, a low renal blood supply, such as occurs with congestive heart failure, leads to reduced glomerular filtration & therefore an elevated BUN. In renal failure, damage to the nephrons, particularly such as occurs with glomerulonephritis or pyelonephritis, leads to decreased glomerular filtration & excretion. As a result, the blood urea nitrogen begins to rise when the glomerular filtration rate falls below 50 mL/min (the normal in an average size man is approximately 125 mL/min).
  
• Postrenal failure resulting from urinary tract obstructions can also cause uremia. Prostatic enlargement is probably the most common cause of urinary tract obstruction.
  
• Other causes of borderline elevated levels of BUN are usually high protein intake & excessive body protein catabolism such as occurs with sepsis or fever, glucocorticoid administration, tetracyclines & gastrointestinal bleeding.

Increases

• uremia

• acute renal failure
• chronic renal failure
• prerenal azotemia

• congestive heart failure

• intrinsic renal failure

• glomerulonephritis
• pyelonephritis

• post obstructive uropathy

• prostatic hypertrophy

• pharmaceutical agents:

• in vivo effects

• alkaline antacids, antimony salts, arsenicals, cephaloridine, furosemide, gentamicin, kanamycin, methyldopa, neomycin

• chemical interferences

• chloral hydrate, chlorobutanol, guanethidine

Specimen

• no special patient preparation is required
• collect whole blood & allow to clot according to manufacturer's instructions
• specimens are collected in a red top vacutainer & should be separated immediately from the cells after collection
• minimum sample size 0.5 mL: with an optimum size of 1.0 mL or larger

More General Terms

• urea in body fluid
• renal function tests; renal function panel

Additional Terms

• urea (carbamide)

References

1. Kodak Ektachem 700 Analyzer Operator's Manual, Kodak Clinical Products, Rochester, New York.
2. Kodak Ektachem Slide Package Inserts, Kodak Clinical Products Rochester, New York.
3. Kodak Ektachem Training Manual, Kodak Clinical Products, Rochester, New York.
4. Tilkian, Conover, & Tilkian: Clinical Implications of Laboratory Tests, C. V. Mosby Company, St. Louis, Mo, p. 18, 1979.
5. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 620.
6. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 12.

urea in serum (BUN)