Clinical approach to the icteric cat (Proceedings)

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Clinical approach to the icteric cat (Proceedings)

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Aug 01, 2011

Icterus occurs when bilirubin accumulates in the plasma and tissues to the extent that it causes visible yellow discoloration of the sclera, mucous membranes, and skin. This occurs when:
     bilirubin > 2 mg/dl (Normal 0.0–0.3mg/dl)

     • Feline Bilirubin Metabolism
          o Bilirubin is a heme breakdown product, produced mostly in the spleen. Carrier proteins transport bilirubin into the liver, where it is conjugated and excreted in the bile.
          o Cats are deficient in glucuronyl transferase necessary for bilirubin conjugation
          o Anorexic cats develop deficiency in protein uptake carriers and intracellular protein ligands for bilirubine
          o Taurine is necessary for bile acid conjugation – deficiency results in cholestasis
          o Bilirubinuria is always significant because there is no renal conjugation of bilirubin in cats, and the renal threshold for bilirubin is higher than that of dogs.

Clinically, we divide causes of jaundice into three large categories – pre-hepatic, hepatic, and post-hepatic

     • Pre-hepatic causes
          o Excessive RBC hemolysis
          o Mycoplasma Haemophilus
          o Oxidative injury
     • Hepatic Causes
          o Hepatitis
          o Cholangiohepatitis
          o FIP
          o Toxoplasmosis
          o Lymphoma
          o Cellular stress
          o Hepatic necrosis
               • Methimazole therapy
     • Post-hepatic Causes
          o Pancreatitis
          o Neoplasia
          o Cholelithiasis
          o Liver flukes
          o Cholangitis
          o Ruptured gall bladder or bile duct