Liver Function Tests

Question 1

What are the 2 primary reasons for checking LFTs?

Answer 1

• To confirm clinical suspicion of potential liver injury or disease.
• To distinguish between hepatocellular injury (hepatic jaundice) and cholestasis (post-hepatic/obstructive jaundice).

Question 2

What does serum albumin tell you?

Answer 2

Marker of synthetic function and useful for assessing severity of chronic liver disease.

Question 3

What does serum bilirubin tell you?

Answer 3

Almost always unconjugated bilirubin. In liver disease, elevated serum bilirubin is usually accompanied by other biochemical abnormalities.

Question 4

What does prothrombin time tell you?

Answer 4

Marker of synthetic function. Sensitive indicator for acute and chronic liver disease.

Question 5

What would raised AST indicate?

Answer 5

High levels in hepatic necrosis, MI, muscle injury and congestive cardiac failure.

Question 6

What would raised ALT indicate?

Answer 6

Cortisol enzyme more specific to the liver. Rise only occurs with liver disease.

Question 7

What would raised ALP indicate?

Answer 7

Raised in both intrahepatic and extrahepati cholestatic disease of any cause, due to increased synthesis.

Question 8

What would raised GGT indicate?

Answer 8

Microsomal enzyme. Its activity can be indicated by many drugs (phenytoin, warfarin and rifampicin) and alcohol.

Question 9

What are the urine tests which can be done to assess liver function?

Answer 9

• Dipsticks for bilirubin or urobilinogen.
• Bilirubinuria due to the presence of conjugated bilirubin. Found in patients with jaundice due to hepatobiliary disease, but is absent if unconjugated bilirubin is the major cause of jaundice.
• The presence of urobilinogen in urine suggests haemolysis or hepatic dysfunction.

Question 10

Describe the use of USS in assessing the liver.

Answer 10

• Allows visualisation of the liver and biliary tree.
• Useful for:
  
  • Detection of extrahepatic obstruction
  • Assessment of jaundiced patient (to exclude obstruction)
  • Assessment of hepatomegaly / splenomegaly
  • Detection of gallstones
  • Identification of cirrhosis (in advanced - liver edge is irregular and spleen is often enlarged)
  • Assessment of lymph node enlargement

Question 11

Why would you CT the liver?

Answer 11

For precise characterisation of a lesion and its vascular supply.

Question 12

Why would you MRI the liver?

Answer 12

MRI is the most sensitive investigation for focal liver disease but can also assess fibrosis.

Question 13

Why would you use colour doppler USS of the liver?

Answer 13

Colour doppler USS demonstrates vascularity within a lesion, and direction of portal and hepatic vein blood flow.