Interpreting liver biochemistry

Question 1

What causes raised unconjugated bilirubin?

Answer 1

Pre-hepatic conditions cause raised unconjugated bilirubin and no bilirubinuria
This can be due to haemolytic anaemias or due to decreased uptake of unconjugated bilirubin across the liver membrane

Question 2

What causes levels of both conjugated and unconjugated bilirubin to rise?

Answer 2

If there is a hepatobiliary problem in the liver

Question 3

What causes raised conjugated bilirubin?

Answer 3

Post-hepatic problems such as bile outflow obstruction. e.g. carcinoma, sclerosing cholangitis
This also causes bilirubinuria

Question 4

What do ALT and AST indicate?

Answer 4

AST is 50% cytosolic and 50% mitochondrial whereas ALT is always cytosolic
AST is released quickly in liver damage. ALT has more of a chronic release and is often present in fatty liver

Question 5

What are the two enzymes that indicate cholestasis?

Answer 5

ALP and gamma GT

Question 6

What does raised gamma gt show?

Answer 6

It mirrors ALP and shows that the cholestasis is of hepatic origin

Question 7

What other proteins can be measured other than ALP,ALT,AST and gamma GT to indicate liver disease?

Answer 7

Albumin can show liver dysfunction if low

INR can reflect the production of clotting factors from the liver

Question 8

What is the AST:ALT ratio and what is normal for it?

Answer 8

It is normally around 0.8 and being greater than 1.0 indicates cirrhosis