Jaundice (Icterus)

  • this is a staining of the tissues with bilirubin or bilirubin complexes
  • bile pigments have a strong affinity for elastic tissue and thus the yellowish colour can be easily seen in the sclera and mucous membranes in life and in the aorta at necropsy
  • the serum bilirubion level gives an indication of the degree of icterus
    • dog's normal range is usually below 0.5mg/100ml
    • level is at least 2mg/100ml when jaundice is clinically evident

Causes

  • overproduction of bilirubin
    • eg haemolytic crises
  • diffuse liver disease
    • where there is a decreased uptake, conjugation, and secretion of bilirubin
  • reduced outflow of bile into the gut
    • intrahepatic biliary obstruction eg foreign bodies, tumours, or fibrosis

Classification types

Haemolytic jaundice

  • due to increased red cell destruction
    • results in increased amounts of bilirubin in the reticuloendothelial system
    • the production may be at a rate which exceeds the capacity of the liver to conjugate and eliminate it
  • most of bilirubin is unconjugated
  • bile pigment is not excreted in the urine
    • since the kidney can excrete only the water soluble conjugate
  • diseases
    • Babesiosis
    • isoimmune reactions eg newborn foal whose dam has elaborated specific antibody against its red cells

Obstructive jaundice

  • due to bile duct obstruction
  • accumulation of conjugated bilirubin
  • bile pigment is excreted in the urine
  • bile pigment will be diminished in the faeces
  • diseases
    • carcinoma involving the head of the pancreas

Hepatocellular jaundice

two factors are concerned in the production of jaundice following liver cell damage

  • damage to liver cells can interfere with the passage of bile along the bile capillaries
    • eg intrahepatic obstruction
  • Liver cell damage may cause failure of conjugation and therefore excretion failure of bile pigment