Differential Diagnosis: Icterus in Cats

Following are differential diagnoses for cats presented with increased icterus.

Prehepatic causes (hemolysis)

• Immune-mediated hemolytic anemia, primary or secondary

  • Blood transfusion

• Non-immune–mediated cause

  • Drug-induced

  • Erythrocyte fragmentation (eg, hemangiosarcoma) 

  • Erythrocyte membrane or enzyme defects (hypophosphatemia, pyruvate kinase deficiency) 

  • Infectious disease

  • Paraneoplastic syndrome

  • Toxin exposure (eg, onion, garlic)

Hepatic causes (hepatocellular dysfunction)

• Fibrosis

• Hepatic lipidosis

• Inflammatory or infectious hepatopathy (hepatitis/cholangiohepatitis)

• Neoplasia  

• Toxin or drug hepatopathy

Posthepatic causes (cholestasis, defective biliary excretion)

• Diseases of the biliary system 

  • Biliary system rupture  

  • Gallbladder disease 

  • Cholelithiasis

  • Stricture

  • Infection (including parasite-induced)

  • Inflammation

  • Neoplasia

• Diseases outside the hepatobiliary system 

  • Enlarged regional lymph nodes

  • Intestinal disease or obstruction

  • Neoplasia (pancreas, duodenum)

  • Pancreatitis

*Bilirubin can be artifactually increased by lipemia and hemolysis

**Serum bilirubin values >1 mg/dL produce serum icterus; values >2 mg/dL produce tissue jaundice