Overview
- Serum bilirubin is a mixture of direct (conjugated) and indirect (unconjugated) bilirubin.
- Peripheral breakdown of red cells and myoglobin → unconjugated bilirubin → (liver) conjugated with glucuronic acid → excreted in bile as conjugated (direct) bilirubin.
- However, conjugated hyperbilirubinemia occurs in even in hemolytic disease.
In animals there is little evidence that the ratio of direct to indirect bilirubin is diagnostically significant.
Uses
In combination
- With total bilirubin
:
- Assessment of liver damage.
- Diagnosis of biliary obstruction.
- With liver enzymes (ALP , ALT , AST or bile acids ) for assessment of liver damage.
Other points
- Icterus may or may not be apparent with increased total or conjugated bilirubin.
- Icterus usually detectable when total bilirubin >2 mg/dl.
- Serum may appear icteric when mucous membranes do not.
Result data
Normal (reference) values
- Normal : 0.-0.2 SI umol/l.
- 1.7-10 umol/l TOTAL bilirubin (normal) (0.1-1 mg/dl).
- Conversion factor: mg/dl x 17.10 → umol/l.
Abnormal values
Increased [direct bilirubin]- Liver damage (toxic, infectious).
- Biliary obstruction/cholestasis.
- Hemolysis.
Sources
Publications
Refereed papers
- Anderson J G & Washabau (1992) Icterus. Comp Cont Educ Pract Vet 14 (8), 1045-1061.
- Engelking L R (1988) Disorders of bilirubin metabolism in small animal species. Comp Contin Educ Pract Vet 10, 712.
Other sources of information
- Ettinger S J & Feldman E C (eds) (2000) Textbook of Veterinary Internal Medicine. 5th edn. Philadelphia: W B Saunders & Co.
- Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.
- Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.
