Hyperbilirubinemia, or elevated blood bilirubin, is a common problem closely associated with liver disease, gallbladder disease, septicemia, and certain autoimmune mediated anemias in our pet companions.
Description of bilirubin and it's function in the body is complicated, so I will just try to glean for you the pertinent facts that you might need to know!!
Relevant laboratory facts about bilirubin:
a. The total bilirubin level provides the most useful clinical information.
b. Jaundice (yellowing of the skin and mucous membranes) develops when bilirubin levels exceed 2.0 mg/dl to 3.0 mg/dl.
c. Bilirubinuria ( bili in the urine), even in concentrated urine, is an abnormal finding in cats. Cats have a high renal threshold for bilirubin, while dogs have a low renal threshold.
d. Bilirubin is less sensitive but more specific than liver enzymes in identifying hepatobiliary disease. Using bilirubin values in conjunction with liver enzymes and serum bile acids concentrations improves the diagnostic specificity of the enzymes.
Total serum bilirubin values are a reflection of RBC destruction, hepatic/liver uptake and conjugation of bilirubin, transfer of bilirubin into caniculi, and a patent/fully functional biliary tree.
There are 3 causes for hyperbilirubinemia: pre-hepatic, hepatic, and post-hepatic.
The chief cause is hemolysis or breakdown and destruction of red blood cells in the peripheral bloodstream. Autoimmune anemias are an example of this. Parasites can cause the redcells to be broken down by the body too....examples would be Babesia and hemobartonella.
Hepatic causes of elevated bilirubin include liver disease (congestion, necrosis, or cholestasis) of any cause. IE: gallbladder obstruction, trauma, viral hepatitis, bacterial hepatitis, cancer of the liver, zinc toxicity, etc.
Post-hepatic causes of elevated bilirubin include extrahepatic bile duct obstruction (EHBDO) or rupture of biliary tract. IE: cancer, gall stones, etc.
So there you have it, the short and not so simple reasons why bilirubin may be elevated in the bloodstream.
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Best Wishes to You and Your Pet!
Dr. Jodi L. Smith