Liver Function Tests

Question 1

Although Liver Function Tests are known as “function” tests, what tests are more telling of liver function and not just biochemistry?

Answer 1

• Prothrombin time

- serum albumin

Question 2

In what 3 states is hypoalbuminaemia seen?

Answer 2

• hypercatabolic states (e.g. chronic inflammation, sepsis)
• excessive renal (e.g. nephrotic syndrome) loss of albumin
• excessive intestinal loss of albumin (intestinal problems with protein loss)

Question 3

What might cause a prolonged prothrombin time?

Answer 3

biliary obstruction due to vitamin K deficiency because vitamin K is poorly absorbed w/o bile salts

Question 4

What are the 4 components tested in the LFTs?

Answer 4

• bilirubin
• Aminotransferases (Aspartate aminotransferase and alanine aminotransferase)
• Alkaline phosphatase
• y-GT (glutamyl transpeptidase)

Question 5

What is bilirubin?

Answer 5

Breakdown product of haemoglobin

Question 6

What is an isolated rise in bilirubin with normal results in LFTs indicative of?

Answer 6

• inherited problem metabolising bilirubin
• inherited haemolysis problems
• inherited erythropoiesis problems (premature death of red blood cell in bone marrow)

Question 7

What is Gilbert’s disease?

Answer 7

Inherited problem with metabolising bilirubin leading to increased bilirubin levels in blood leading to jaundice

Question 8

What is most common cause of hyperbilirubinaemia along with other abnormal LFT results?

Answer 8

biliary tract obstruction

Question 9

What are aminotransferases and when are they raised?

Answer 9

Enzymes in hepatocytes that leak into blood when hepatocytes are injured

Question 10

Very low aminotransferase levels may be found in acute hepatitis. True or false?

Answer 10

False

Question 11

Which aminotransferase is also found in heart and skeletal muscle and so can be raised in M.I./skeletal muscle damage?

Answer 11

Aspartate aminotransferase (AST) -> S-> Skeletal muscle

Question 12

Which aminotransferase is more specific to the liver?

Answer 12

ALT

Question 13

Where is alkaline phosphatase situated in the liver?

Answer 13

Canicular and sinusoidal membranes (canicular membranes line the bile canaliculus which is a thin tube that collects bile from hepatocytes and empties it into the common hepatic duct)

Question 14

What GI related disease can cause raised serum alkaline phosphatase?

Answer 14

Cholestasis (i.e. bile flow obstructed due to impaired hepatocyte secretion or bile duct obstruction)

Question 15

What are 5 non-GI related reasons for raised alkaline phosphatase levels and why?

Answer 15

• pregnancy
• osteomalacia
• growing children
• Paget’s disease (problem with normal bone tissue recycling process)
• bony metastases

WHY?
alkaline phosphatase also found in bones and placenta

Question 16

What other measurement can you use to determine whether raised alkaline phosphatase levels are a result of bone/liver disease?

Answer 16

y-GT serum levels

Question 17

What is y-GT?

Answer 17

liver enzyme

Question 18

Which enzyme is first to show up in high levels in bile duct obstruction?

Answer 18

y-GT (AKA GGT)

Question 19

What may induce y-GT and cause it to be raised?

Answer 19

• alcohol

- enzyme-inducing drugs e.g. phenytoin (med used to treat epilepsy)

Question 20

What is high y-GT a useful screen for?

Answer 20

alcohol abuse

Question 21

What 2 liver enzymes in high levels together indicate cholestasis?

Answer 21

alkaline phosphatase and GGT

Question 22

What are 3 cholestatic disorders that can lead to raised serum alkaline phosphatase and raised serum bilirubin in excess of the liver enzymes?

Answer 22

• primary biliary cirrhosis
• primary sclerosing cholangitis
• extrahepatic bile duct obstruction

Question 23

What is albumin’s function?

Answer 23

• maintains intra-vascular oncotic pressure

- transports water-insoluble substances such as bilirubin and some drugs