Liver function test

Question 1

What are the common liver diseases

Answer 1

1. Hepatitis
2. Liver cirrhosis
3. Tumours

Question 2

What is SAAG and what are the indications of the SAAG gradients

Answer 2

Serum ascities albumin gradient

High gradient: >1.1g/dL indicates portal hypertensionand suggests non peritoneal cause of ascites

Low gradient: <1.1 g/dL indicated peritoneal cause of the ascites

Question 3

Explain a prothrombin time test

Answer 3

It is a test of plasma clotting activity and it is expressed as a ratio to a control value (INR)
This reflects activity of vitamin K-dependant clotting factors synthesized by the liver

Question 4

What does abnormal PT indicate

Answer 4

Acute liver disease can prolong the PT

Vitamin K deficiency can increase PT

Question 5

Why is ALT/AST meassured

Answer 5

Aminotransferases/transaminases - ALT is specific for the liver. It is directly proportional to the amount of hepatocyte necrosis

It indicates hepatocyte disease
- it increases release of ALT/AST into the blood

Question 6

What stage of disease do different levels of aminotransferases indicate

Answer 6

Mild: <5 x ULN
Moderate: <5-10 x ULN
Severe: >10 x ULN
Acute hepatitis: 10-100 x ULN
Chronic hepatitis: >5-10 x ULN

Question 7

What are the surrogate markers of alcoholic liver disease

Answer 7

Elevated GammaGT
AST : ALT >2
Hypertriglyceridaemia
Increased serum IgA concentration
Red cell macrocytosis

Question 8

What are the mechanisms and causes of prehepatic jaundice

Answer 8

In absence of liver disease it is due to hameolysis where the hepatic conjugating enzymes get overwhelmed which leads to an increased overall excretion of bilirubin in stool

This leads to physiological jaundice and kernicterus

Question 9

Explain the presentation of conjugated hyperbilirubinaemia

Answer 9

Water soluble conjugated bilirubin enteric systemic circulation is excreted by kidneys and as a result urine is a deep orange brown colour

No bilirubin enters the gut therefor stools are pale in colour

Question 10

Which two enzymes are meaussured in cholestasis and explain why

Answer 10

Alkaline phosphatase (ALP): Cholestasis stimulates increased production of ALP by biliary epithelium

Gamma-glutamyltransferase: Sensitive for hepatobiliary disease but non-specific

Question 11

What are the common causes of elevated amonia

Answer 11

Urea cycle impaired in liver cirrhosis
High protein meals
GIT bleeding