Approach to jaundice

• Bilirubin

  Jaundice/icterus = hyperbilirubinaemia

  • This is problematic as causes renal tubular damage

  Three main areas that can be overloaded leading to bilirubin build-up:

  • Pre-hepatic - haemoglobin
  • Heptaic - liver intrahepatic biliary tract
  • Post-hepatic - biliary excretion
• Categories of jaundice

  Pre-hepatic:

  • Before the liver.
  • Related to increased haemoglobin destruction

  Hepatic:

  • The liver doesn‘t do its job
  • Reduced conjugation of bilirubin

  Post-hepatic”

  • The conjugated bilirubin can not exit via the biliary system.
• Pre-hepatic jaundice

  Oversupply of precursors (haemoglobin/heme) into the system = increased destruction of red blood cells.

  Haemolytic anaemia:

  • Acquired defects
  • Hypophoshpateamia
  • Oxidative damage - e.g. toxic insults - onion/garlic/paracetomol, metabolic disease
  • Genetic defects
  • Abyssinian and Somali cats hereditary haemolysis
  • Non-spherocytic haemolytic anaemia in beagles.
  • Immune mediated
  • Primary
  • Secondary
• How do we tell if jaundice is pre-hepatic? - haemotology

  Anaemia:

  • Regenerative
  • Macrocytic, hypochromic

  Blood smear:

  • Sperocytosis
  • Auto-agglutination
• How do we tell if jaundice is pre-hepatic? - imaging

  Primarily looking for neoplastic causes of IMHA

  • 3 view CXR, lung and abdominal ultrasound.
  • Advanced imaging - CT with contrast.
• How do we tell if jaundice is pre-hepatic? - serum and urine discolouration

  Haemoglobinaemia

  Haemoglobinuria

  Further bloods/infectious disease screening:

  • Toxin/ drug risk
• Approach to jaundice - hepatic 


  Metabolism and delivery of heme into the system is normal

  The ability of the liver to process the bilirubin and excrete it is poor i.e. the liver is failing in some way, or the intrahepatic biliary tree is damaged/ compressed by the liver around it.

  Infectious (hepatitis)

  • Bacterial, fungal, viral
  • CAV, FIV, FIP, FeLV

  Inflammatory - cholangiohepatitis

  Neoplasia - lymphoma; MCT adenocarcinoma

  Drugs/toxins - paracetamol, NSAIDs

  Degenerative - Amyloids, lipidosis (cats), Cirrhosis

  Proximal biliary disease - cholangitis/cholangiohepatitis
• Approach to jaundice - liver enzymes - ALT

  Part of the pyruvate cycle

  • Inside liver cells
  • Serum elevations are consistent with hepatocellular damage:
  • Dependant on numbers of liver cells present - e.g. cirrhosis may be low/normal.
  • Depends on numbers of cells damaged - e.g. focal neoplasia vs widespread infection.
• Approach to jaundice - liver enzymes - AST

  Found in the liver and muscle (skeletal and cardiac) - often elevated through venepuncture. CK elevations often found concurrently if due to muscle damage.

  • Resultantly many people disregard AST elevations on biochemistry.
• Approach to jaundice - liver enzymes - GGT

  Part of glutathione metabolism and present in biliary tract cells (and pancreas, spleen, heart, brain)

  • Similar to ALP in terms of determining biliary tract disease.
  • Probably more useful in combination as can give false positives alone (especially cats).
• Approach to jaundice - liver enzymes - ALP

  This is widespread in the body but is found in concentrated amounts in the biliary tree. Other - bone, gut, steroid induced.

  • Even small elevations in cats could be significant due to a shorted half life compared to dogs (6h vs 66h)
  • Reactive hepatopathies - hyperadrenocorticism, diabetes mellitus, thyroid disease.
• Approach to jaundice - liver function tests - clotting factors

  Clotting factors - all produced by the liver (excepts VII and vWF) - prolonged aPTT and PT.
• Approach to jaundice - liver function tests - albumin

  Albumin - produced by the liver so low values may support liver disease (<15g/l -> oedema/ascites)
• Approach to jaundice - liver function tests - bile acid stimulation (BAST)

  This will assess liver function and biliary flow -> bile acids are synthesised in the liver, secreted into the bile and moved in the duodenum. Reabsorbed from the GI tract and return to the liver via the portal vein to be recycled and re-excreted into the gall bladder - entero-hepatic recycling.

  • This means these are an excellent test of liver function and/or biliary tract disease, but they are poor at differentiating between hepatic and post hepatic jaundice.
• Approach to jaundice - liver function tests - urea

  Urea - end product of protein metabolism and ammonia production; low values support reduced liver function.
• Approach to jaundice - liver function tests - ammonia

  Ammonia - considering the above, ammonia may therefore be high - vary labile so need point of care testing to test quick enough.
• Post-hepatic jaundice

  Delivery/ metabolism of heme is normal.

  Conjugation and excretion of bilirubin by the liver is normal.

  The bile duct is no longer transporting it away -> back pressure and exudation back into the system.

  Realistically this is most likely to be an obstruction = extrahepatic bile duct obstruction (EHBDO).
• Post-hepatic jaundice EHBDO - intraluminal obstruction

  Cholelithiasis (stones)

  Gall bladder Mucocoele (border terriers)

  Inspissated bile

  Gall bladder polyps

  Cysts (cats)
• Post-hepatic jaundice EHBDO - extramural

  Pancreatic disease

  • Pancreatitis
  • Pancreatic neoplasia

  Duodenal disease

  • Infectious
  • Inflammatory
  • Neoplastic

  Porta hepatitis stricture
• Post-hepatic jaundice EHBDO - mural

  Inflammatory swelling

  • Cholangitis
  • Cholecystitis
  • Choledochitis

  Neoplasia