Jaundice and LFTs

Question 1

What is jaundice?

Answer 1

Clinical manifestation of raised bilirubin

Question 2

How is Bilirubin recycled?

Answer 2

Bilirubin is the breakdown product of haem is its unconjugated state and bound to albumin.

Bilirubin is then conjugated in the liver and it makes it water soluble.

It is then excreted in urine and faeces.

Question 3

How can the causes of jaundice be classified?

Answer 3

Pre-hepatic
Hepatic
Post-hepatic

Question 4

What is pre-hepatic jaundice?

Answer 4

Caused by increased degradation of haemoglobin

• Liver conjugating ability is fine
• Excretion pathway is fine

Too much demand on the liver.

Therefore, the levels of bilirubin that are raised tend to be unconjugated.

Question 5

What are some common causes of pre-hepatic jaundice?

Answer 5

Haemoglobinopathy:

• Sickle cell
• Thalassaemia
• Spherocytosis

Damage to red blood cells - Haemolysis

Question 6

What is hepatic jaundice?

Answer 6

This is caused by reduced conjugating ability of the liver.

• Damage to hepatocytes
• Amount of bilirubin is fine
• Excretion pathway is usually fine

Therefore you get a mixture of conjugated and unconjugated bilirubin

Question 7

What are some common causes of hepatic jaundice?

Answer 7

Cirrhosis (causes hepatocyte necrosis):

• Alcoholic liver disease
• Viral hepatitis (B and C)
• Medications (Hepatotoxic - methotrexate)
• Autoimmune hepatitis
• Hereditary haemochromatosis
• Wilson’s disease

Acute liver damage:

• Paracetamol toxicity
• Viral hepatitis (A,D,E)
• Other infections

Question 8

What is post hepatic jaundice?

Answer 8

This is caused by obstruction to the excretion pathway

• Amount of bilirubin is fine
• Conjugating ability of the live is fine

Therefore raised bilirubin tend to be conjugated (water soluble)

Question 9

What can high levels of conjugated bilirubin lead to?

Answer 9

Dark urine and pale stools.

This is because bilirubin is pigmented and conjugated bilirubin is water soluble so, without it you get pale stools.

Question 10

What are some common causes of post-hepatic jaundice?

Answer 10

Gallstones

Any intrahepatic pathology compressing the bile ducts

• PBC -primary biliary sclerosis
• PSC -primary sclerosing cholangitis
• Malignancy

Biliary stricture

Pathology of the head of the pancreas - can cause obstruction because of location.

Question 11

What are the liver function tests?

Answer 11

Bilirubin (conjugated vs unconjugated)
Albumin 
ALT
AST
ALP - alkaline phosphatase

Question 12

What is albumin?

Answer 12

Major serum protein

This assesses synthetic function of the liver - if the liver is reduced, it makes less albumin, usually seen in chronic cases.

Low albumin contributes to ascites

Low albumin can also be caused by damage to kidney - nephrotic syndrome

Question 13

What are ALT and AST? What is the difference?

Answer 13

These are hepatic enzymes - if hepatocytes are damaged, these enzymes will go up.

ALT is more specific to the liver - AST is also found in cardiac/skeletal muscle and red blood cells.

ALT rises more than AST in acute liver damage

AST rises more than ALT in cirrhosis and alcoholic hepatitis

Question 14

What is ALP?

Answer 14

Alkaline phosphatase

Found in the cells lining the bile ducts - levels therefore go up in cholestasis (bile duct obstruction)

ALP can also be increased in bone diseases - as more when increased bone turnover.

You use Gamma-Glutamyl Transferase (Gamma GT) to make sure that the liver is the source.

Question 15

If you have pre-hepatic jaundice, what are your LFTs?

Answer 15

Raised unconjugated bilirubin
Associated anaemia
Other LFTs NAD

Question 16

If you have hepatic jaundice, what are your LFTs?

Answer 16

Mixd biliubin
High ALT and AST
Normal ALP or slightly elevated

Question 17

If you have post-hepatic jaundice, what are your LFTs?

Answer 17

Raised levels of conjugated bilirubin

Raised ALP - associated increase in y-GT