Jaundice and LFTs

Question 1

What is jaundice?

Answer 1

The clinical manifestation of raised bilirubin.

Question 2

How does jaundice present?

Answer 2

Yellowing of the skin and sclera.

Question 3

What is bilirubin?

Answer 3

A breakdown product of haem. It’s unconjugated state is bound to albumin. It is excreted in urine and faeces.

Question 4

How is bilirubin metabolised?

Answer 4

Haemoglobin in the erythrocyte is broken down by splenic macrophages in the spleen. This forms global and haem. Haem is further broken down to unconjugated bound to albumin bilirubin. This is carried in the blood to the liver where it is conjugated and removed as urobilinogen from the kidneys as urine and the gut as faeces.

Question 5

What are the 3 types of jaundice?

Answer 5

1. Pre-hepatic: too much haem.
2. Hepatic: reduced hepatocyte function.
3. Post-hepatic: Obstructive causes.

Question 6

Describe Pre-hepatic jaundice.

Answer 6

Caused by increase degradation of haemoglobin. Thus liver conjugation and excretion pathway is fine. There is too much demand on the liver and thus the levels of bilirubin that are raised tend to be unconjugated.

Question 7

What are the common causes of pre-haptic jaundice?

Answer 7

Haemoglobinopathies:
1. Sickle cell.
2. Thalassaemia.
3. Spherocytosis.
Damage to RBCs:
4. Haemolysis.

Question 8

Describe Hepatic jaundice.

Answer 8

Caused by reduced conjugating ability of the liver due to damage to the hepatocytes. The amount of bilirubin is ok and the excretion pathway is usually fine and thus you get a mixed picture of conjugated and unconjugated bilirubin.

Question 9

What are the common causes of Hepatic Jaundice?

Answer 9

1. Paracetamol Toxicity.
2. Alcoholic Liver Disease.
3. Non-Alcoholic Fatty Liver Disease.
4. Hereditary Haemochromatosis.
5. Viral Hepatitis.
6. Other infections.
   Some of these are acute.

Question 10

Describe Post-hepatic jaundice.

Answer 10

Caused by an obstruction to the excretion pathway, with the amount of bilirubin being fine and the conjugating ability of the liver being fine. Therefore the raised bilirubin tends to be conjugated.
Bilirubin is pigmented, conjugated bilirubin is water soluble. This means more is going to be excreted by the kidneys so there will be dark urine and pale stools.

Question 11

What are the common causes of Post-hepatic jaundice?

Answer 11

1. Gallstones.
Pathology compressing the bile ducts:
2. Primary Biliary Cirrhosis (PBC).
3. Primary Sclerosing Cholangitis (PSC).
4. Malignancy.
5. Biliary stricture.
6. Pathology of the head of the pancreas-> pancreatic carcinoma.

Question 12

Give examples of Liver Function Tests.

Answer 12

1. Bilirubin: conjugated vs unconjugated.
2. Albumin.
3. Alanine Transaminase (ALT).
4. Aspartate Transaminase (AST).
5. Alkaline Phosphatase (ALP).

Question 13

Describe albumin as a LFT.

Answer 13

Albumin is a major serum protein which is used to assess synthetic function of the liver as it is made in the liver. If liver function is reduced it’ll make less albumin, which is usually seen in chronic cases.
Low albumin contributes to ascites.
Other proteins are also made in the liver and can be used to measure synthetic function of the liver.

Question 14

Describe ALT and AST as a LFT.

Answer 14

They are hepatic enzymes which if the hepatocytes are damaged will leak out and cause the levels in the blood to go up.
ALT is more specific to the liver as AST is also found in the cardiac/skeletal muscle and red blood cells.

Question 15

What happens to ALT and AST in acute liver damage?

Answer 15

ALT rises more than AST in acute liver damage.

Question 16

What happens to ALT and AST in cirrhosis and alcoholic hepatitis?

Answer 16

AST rises more than ALT ion cirrhosis and alcoholic hepatitis.

Question 17

When will ALP go up?

Answer 17

Alkaline phosphatase is found in the cells lining the bile duct and so will go up in cholestatis (bile duct obstruction).

Question 18

What is the alternative for ALP measuring and why is it done?

Answer 18

There are other reasons it can go up so gamma glutamyl transferase sometimes used.

Question 19

How does LFTs link to Pre-hepatic jaundice?

Answer 19

There will be raised levels of unconjugated bilirubin.

It is associated with anaemia.

Question 20

How does LFTs link to Hepatic jaundice?

Answer 20

Likely to see a mix of unconjugated and conjugated bilirubin.
High levels of ALT and AST.
Normal ALP (could be slightly elevated).

Question 21

How does LFTs link to Post-hepatic jaundice?

Answer 21

Raised levels of conjugated bilirubin.

Raised ALP-> associated increase in Gemma glutamyl-transferase.