Overview

• Derived from breakdown of creatine in muscle.
• Excreted by kidneys.
• Not influenced by protein metabolism (unlike urea).
• Important marker of renal function; levels controlled by excretion rate.
• Plasma concentration also depends on muscle mass.

Sampling

Tests

Methodologies

• Colorimetric method: reaction between alkaline picrate solution and creatinine.
• Non-creatinine chromagens and other compounds also may react with alkaline picrate solution.
• Enzymatic method: no artifacts caused by chromagens.

Availability

• Widely available.

Validity

Sensitivity

• Better indicator of glomerular filtration rate (GFR) than BUN, but increases in serum creatinine are not in proportion to the decrease in GFR.
• Low sensitivity for detection of renal disease (especially if poor body condition and muscle mass).
• Must be used in conjunction with other tests especially urine specific gravity.

Specificity

• Low specificity for detection of renal disease in well-muscled dog breeds (eg greyhounds).
• Must be used in conjunction with other tests especially urine specific gravity.

Technique (intrinsic) limitations

• Interpret in conjunction with other laboratory and clinical findings.

Result Data

Further Reading

Publications

Refereed papers

• Recent references from VetMedResource and PubMed.

Other sources of information

• Internation Renal Interest Society, IRIS Staging of CKD: http://www.iris-kidney.com.
• 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.