Liver Function Tests

Question 1

Terminology

Answer 1

Chol - Bile
Cholengeo - Bile duct
Cholcyst - Gall bladder

Question 2

Liver Functions

Answer 2

1. Excretes bile for food digestion - some drains to duodenum and rest is stored in the gall bladder
2. Carbohydrate metabolism - gluconeogenesis, glycogenosis, glycogenolysis
3. Break down of insulin and other hormones
4. Lipid metabolism - cholestrol synthesis and triglycerides production
5. Produces coagulation factors and plasma protein i.e. albumin
6. Breaks down haemoglobin, toxic substances and most medicinal products
7. Converts ammonia to urea
8. Storage of fat soluble vitamins (A, D, E and K), vitamin B12, iron, copper and glycogen
9. From 1st trimester - 42nd week it is responsible for red blood cell production thereafter the bone marrow takes control

Question 3

Liver function tests

Answer 3

Used to differentiate diagnosis of liver disease and injury
Provides results for
- Bilirubin
- Aminotransferases (AST/ALT)
- Alkaline phosphotases (ALP) and gamma glutamyl transferases (GGT)

Question 4

Bilirubin

Answer 4

Hameoglobin breakdown > Unconjucated bilirubin bound to albumin > Unconjugated bilirubin enters liver > Conjugated by glucuronic acid > enters gut > gives the brown colour to stools

• Poo without bilirubin is yellow
• Jaundice yellow skin, yellow eyes indicates jaundice
• Exchange transfusion for babies with high bilirubin
• Normal concentration is < 17 micomol/L

Question 5

High conc. of Bilirubin

Answer 5

• Hameolysis
• G6DP deficiency
• Immature conjugating system (newborns)
• Failure of conjugating mechanism
• Viral hepatitis
• Paracetamol overdose
• Cholestasis by gallstones
• Gilbert syndrome - genetation in UDP-Glucuronide transferase

Question 6

Aminotransferases

Answer 6

AST (10-40) ALT (5-40)
ALT mainly localised in liver
AST found in heart, skeletal, muscle, kidney, brain and liver tissues
- Found in any form of acute liver damage
- Found in hepatocytes
- Increases seen in obstructive jaundice and cirrhosis
- AST:ALT in 2:1 in alcoholic liver disease

Question 7

Alkaline Phosphotase

Answer 7

30-300

• Found in membrane
• Main indicator of cholestasis (blockage in the flow of bile)
• High ALP in presence of tumours and cirrhosis
• Serum levels raise in pregnancy
• Derived from bone
• Differentiation from cholestasis is presence of GGT

Question 8

GGT Gamma glutamyl transpeptidases

Answer 8

Microsomal enzyme distributes in liver tissues and renal tubules
- High GGT induced by alcohol or any drug that induce CYP450

Question 9

Albumin

Answer 9

35-48
Half-life=3 weeks
Indicator of chronic liver disease
i.e. cirrhosis
Hypoalbuminaemia means low oncotic pressure leading to water circulating from circulation to peritoneal cavity - ASCITES
- Albumin may not effect liver if there are no other LFT factors

Question 10

Ascites

Answer 10

EXCESSIVE FREE FLUID IN PERITONEAL CAVITY

• Sodium and water retention (RAAS system kicks in)
• Decreased oncotic pressure due to reduced albumin synthesis
• Portal hypertension

Treat with spironolactone = Furesomide, Amiloride
Low salt intake
Bed rest

Question 11

Prothrombin time

Answer 11

Clotting time

• Indicator of hepatic synthetic function
• Not abnormal until 80% is lost
• Parental vitamin K will reverse abnormality

Question 12

Alfa-fetoprotein (AFP)

Answer 12

• Synthesised by foetal liver

- Presence during pregnancy indicates baby has neural tube defect

Question 13

Ammonia

Answer 13

• Hepatic encephalopathy
• Reye’s syndrome
• Treat with lactulose and antibiotic (neomycin)
• removes precipitating factors

Question 14

Hepatic encephalopathy

Answer 14

Altered mental functional state with liver impairment

Question 15

Spider naevus

Answer 15

• Blood vessels expand

- Lack of metabolism of oestrogen

Question 16

Drug prescribing

Answer 16

1. Impaired metabolism 
Rifampicin, fusidic acid
2. Drugs highly bound to albumin
Phenytoin, prednisolone
3. Reduced Clotting
Oral anti-coagulants
4. Hepatic encephalopathy
Sedative, opioid analgesics, diuretics, anti-muscaranics, drugs causing constipation
5. Ascites
NSAID's corticosteroids

Question 17

Biomarkers results

Answer 17

Increased AST and ALT = Acute viral hepatitis
Increased ALP and GGT = Cholestasis
Increased GGT and AST:ALT>2:1 = Alcoholic liver disease
Decreased albumin and prothrombin time = Chronic liver disease i.e. Cirrhosis
Increased bilirubin = Acute viral or drug-induced hepatitis or cholestasis