Creatinine
Indications for performing this test: This test is part of a basic
serum chemistry panel and is used with BUN to
evaluate kidney function.
Creatinine is a nonprotein-nitrogen metabolite of muscle
metabolism. It is freely excreted by glomerular filtration, and is not reabsorbed by
the renal tubules. Serum creatinine is therefore a much better indicator of
glomerular filtration rate than is BUN. Creatinine will increase as the glomerular
filtration rate decreases. Any elevation of nitrogen containing products in the blood
is called azotemia.
Interpretation of elevated creatinine:
- Creatinine does not become significantly elevated with diet
unlike BUN, but is affected by muscle mass.
|
|
- Prerenal azotemia - Some causes include:
increased protein catabolism (high protein diet), corticosteroids, necrosis, starvation, prolonged
exercise, infection, fever, or decreased renal perfusion due to shock, dehydration
or
cardiovascular disease.
|
|
- Renal azotemia - Occurs after about 3/4 of the nephrons
are nonfunctional. Renal azotemia can occur in both acute renal failure (AFR)
and chronic renal failure (CRF).
|
|
- Postrenal azotemia - Usually due to obstruction or
postrenal leakage. May be differentiated due to the accompanying clinical signs of
oliguria or anuria, though these signs can also occur with renal azotemia.
|
|
Important Species Differences:
- Dogs have some tubular excretion of creatinine.
- Creatinine is a more sensitive indicator of renal disease than BUN in
the cow and the horse because there is less potential for gastrointestinal
excretion.
For more information . . .
- Veterinary Laboratory Medicine, Duncan, Prasse, and Mahaffey
page 179-180.
- Veterinary Laboratory Medicine, Interpretation & Diagnosis.
Meyer & Harvey, pages 331.
