GI12 - Jaundice & Liver Function Tests

Question 1

4 liver function tests

Answer 1

1.) Bilirubin - conjugated vs unconjugated

2. ) Albumin - asseses synthetic function of the liver
   - if liver function is reduced, it makes less albumin
   - low albumin contributes to ascites
3. ) ALT and AST - alanine transaminase and aspartate transaminase are hepatic enzymes
   - if hepatocyes are damaged, the enzymes levels go up
   - ALT is more specific to the liver becasue AST is also found in cardiac/skeletal muscle and in RBCs
   - ALT rises > AST in acute liver damage
   - AST rises > ALT in chronic liver damage
4. ) ALP - alkaline phosphatase
   - found in cells lining the bile ducts so levels go up in bile duct obstruction (cholestasis)
   - other cause of raised ALP is increased bone turnover

Question 2

4 features of pre-hepatic causes of jaundice

Aetiology
Bilirubin Levels
Other LFTs
Common Causes x2

Answer 2

1. ) Aetiology - increased degradation of haemoglobin
   - liver conjugating ability and excretion pathway is fine
   - often associated with anaemia
2. ) Bilirubin Levels - raised unconjugated bilirubin
3. ) Other LFTs - normal
4. ) Common Causes - RBC breakdown
   - haemoglobinopathies: sickle cell, thalassaemia, spherocytosis
   - RBC damage - haemolysis (haemolytic anaemia)

Question 3

4 features of hepatic causes of jaundice

Aetiology
Bilirubin Levels
Other LFTs
Common Causes x2

Answer 3

1. ) Aetiology - reduce hepatocyte function
   - amount of bilirubin and excretion pathway is fine
   - sometimes, obstruction can lead to reduced hepatocyte function so you see a ‘mixed picture’
2. ) Bilirubin Levels - raised conjugated and unconjugated
   - damage to hepatocytes reduces conjugating ability
   - some parts are fine whilst other parts are damaged
3. ) Other LFTs - raised ALT/AST (hepatocyte damage)
   - normal ALP (no obstruction)
4. ) Common Causes - hepatocyte damage
   - cirrhosis, acute liver damage (infections, toxicity etc)

Question 4

5 features of post-hepatic causes of jaundice

Aetiology
Bilirubin Levels (+ excretion)
Other LFTs
Symptoms of Obstructive Jaundice
Common Causes (2 groups)

Answer 4

1. ) Aetiology - obstruction to excretion pathway
   - amount of bilirubin and conjugating ability is fine
2. ) Bilirubin Levels - raised conjugated bilirubin
3. ) Other LFTs - raised ALP, normal ALT/AST
4. ) Symptoms of Obstructive Jaundice - bilirubinuria
   - dark urine: conjugated bilirubin is water soluble so can be excreted via urine and is pigmented (dark)
   - pale stools: ↓stercobilin (usually colours stool)
   - steatorrhoea: ↓bile due to blockage if biliary tract
5. ) Common Causes - blockage of ducts
   - extra-hepatic: gallstones, biliary stricture, pathology of head of the pancreas (e.g. pancreatic carcinoma)
   - intrahepatic pathology compresses intraheptic bile ducts: oedema (inflammation), cirrhosis, malignancy