Liver Function

Question 1

What is involved in the normal function of the liver?

Answer 1

• Intermediary metabolism
• Xenobiotic metabolism
• Protein synthesis
• Bile synthesis
• Reticulo-endothelial function (immune modulating)

Question 2

What is intermediary metabolism?

Answer 2

It is an enzyme controlled process that extracts energy and uses it to construct cellular components.

Question 3

In liver failure, why can a patient become encephalopathic?

Answer 3

There is increased ammonia, which is encephalotoxic

Question 4

What enzyme is involved in many of the xenobiotic functions of the liver?

Answer 4

Cytochrome P450

Question 5

What is the function of bile?

Answer 5

• Excretion
• Micelle formation
• Digestion

Question 6

In a liver function test, what is measured?

Answer 6

Liver cell damage:

• AST and ALT
• AlkPhos
• GGT
• Bilirubin
• AFP

Liver function:

• Clotting factors
• Albumin
• Glucose

Question 7

What is the function of the aminotransferases?

Answer 7

They are involved in amino acid metabolism

Question 8

Where can aminotransferases be found? What is the normal level? When can they be raised?

Answer 8

They are predominately found in hepatocytes, but can be found in the muscle, brain and kidneys.

The normal level is less than 40iu/L.

They can be raised in hepatocellular death.

Question 9

How can the relative levels of the aminotransferases specify the cause of hepatocellular death?

Answer 9

If AST:ALT is >2 this is likely alcoholic.
If it is above this with no alcohol history, it is likely cirrhosis.

If AST:ALT is <1.1, it is likely viral damage.

Question 10

What is the function of alkaline phosphatase?

Answer 10

This is largely unknown.

Question 11

What is the normal level of ALP? When can it be raised?

Answer 11

It is normally between 30 and 150 iu/L.

It can be raised in cholestasis and bone disease. It is also raised in pregnancy and malignancy.

Question 12

What is gamma-glutamyl transferase involved in?

Answer 12

It is involved in amino acid metabolism.

Question 13

What is the normal level of GGT? When can it be raised?

Answer 13

It is normally between 30 and 150 iu/L.

It is raised in chronic alcohol use. It can also be raised in bile duct disease and metastasis.

Question 14

What is the role of albumin?

Answer 14

It is primarily involved in controlling the oncotic pressure of blood.

Question 15

When can albumin levels be low?

Answer 15

• Low production (liver disease)
• Loss of albumin (renal or GI loss)
• Sepsis (capillary leakage)

Question 16

Why can clotting factors be a better marker than albumin for acute disease?

Answer 16

The half life of clotting factors is much shorter (albumin is 20 days, clotting factors are mere hours) so any change can be detected far closer to a change in pathology.

Question 17

What is the role of alfa fetoprotein?

Answer 17

It is primarily involved in foetal immune modulation. In adults, its purpose in unclear.

Question 18

When can alfa fetoprotein be raised?

Answer 18

It is raised in hepatocellular carcinoma, and is a good cancer marker for testicular cancer as well. It is also raised in pregnancy.

Question 19

In raised bilirubin, what is the best way to consider the pathology involved?

Answer 19

Consider the rest of the liver function test:

Normal hepatic enzymes:

• Haemolysis
• Gilbert’s syndrome

Raised ALP:

• Obstructive jaundice (gall stones, pregnancy)
• Non-obstructive jaundice (PBC, PSC)

Raised AST/ALT:
- Acute or chronic hepatocellular damage

Question 20

What is the significance of pale stools and dark urine when considering a raised bilirubin?

Answer 20

This shows the jaundice is obstructive, giving this clinical picture.

Question 21

What is the ‘liver panel’?

Answer 21

These are further tests that can be made when the liver function test is unclear. It involves:

• Hepatitis screen
• CK, TFTs
• Alpha-1-antitrypsin
• Immunoglobulins

Question 22

In a patient with a raised ALT, what must be considered when discussing management?

Answer 22

You must look at the other markers in the LFTs.

If isolated raised ALT:
- Discuss lifestyle changes

If symptomatic/unisolated raised ALT:

• Conduct liver function tests and liver screen to determine cause
• Treat the cause