Liver Flashcards
How is bilirubin formed?
Haemoglobin broken into haem and globin
Haem is metabolised by haem oxegenase to produce iron and biliverdin, and the biliverdin is then reduced by biliverdin reductase to give bilirubin
What colour is biliverdin?
Green
What colour is bilirubin?
Yellow
How is bilirubin transported?
Initially binds to albumin and is transported to liver
95% is unconjugated before passed to liver
How is bilirubin conjugated?
Hepatic uptake, trasnported into hepatocytes
Binds to LIGANDIN
Transferred to endoplasmic reticulum and is conjugated
Bilirubin becomes BILIRUBIN DIGLUCORONIDE (soluble)
How is bilirubin excreted?
Conjugated bilirubin goes into bile, and is degraded to UROBILINOGEN in the small intestine (colourless)
Transformed into STERCOBILIN (brown and is excreted)
(not all urobilinogen is excreted, some is oxidised in kidneys to become yellow urobilinogen)
When is bilirubin detectable as jaundice?
> 50 umol/L
Causes of raised unconjugated bilirubin? (pre hepatic jaundice)
Physiological neonatal due to high RBCs
Haemolysis
Gilbert syndrome
Crigler-Najaar syndrome
Features of pre hepatic jaundice? (recognise)
Mild AST and LDH increases
Decreased haptoglobin if haemolysis
Increased reticulocytes
How do urine and stools look with high levels of conjugated bilirubin?
Dark, as conjugated bilirubin leaks into systemic circulation and is excreted in urine
Pale stools as no stercobilin is formed in obstruction
Causes of hepatitic jaundice (4)
Hepatitis
Cirrhosis
Infiltrations eg sarcoidosis
PBC
Causes of post hepatic jaundice (4)
Gallstones
Biliary stricture
PSC
Cancer of pancreatic head or biliary tree
Which is more liver specific, AST or ALT?
ALT
AST found in many cells and will be elevated with haemolysis or muscle damage
Causes of raised AST and ALT
Glucose Lipids Viruses Drugs Autoimmune disease Wilsons Haemochromotosis
AST:ALT ratio in NAFLD?
<1, ALT is predominently raised
