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Data Interpretation > Liver Function Test > Flashcards

Liver Function Test Flashcards

1
Q

Why is a liver function test performed?

A
  1. To confirm a clinical suspicion of liver injury or disease
  2. To distinguish between hepatocellular injury (hepatic jaundice) and cholestasis (post-hepatic or obstructive jaundice)
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2
Q

What are the liver function test reference ranges?

A 
ALT	3-40 iu/l
AST	3-30 iu/l
ALP	3-100 umol/l
GGT 8-60 u/l 
Bilirubin	3-17 umol/l 
Albumin	35-50 g/l 
PT 10-14 seconds
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3
Q

What is alanine transaminase (ALT) ?

A

A marker of hepatocellular injury.

Found in high concentration within hepatocytes and enters the blood following hepatocellular injury

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4
Q

What is Alkaline Phosphatase ?

A

A protein that is concentrated in the liver, bile duct and bone tissues.

Is raised in liver pathology due to increased synthesis in response to cholestasis

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5
Q

What does a >10 fold increase in ALT and < 3 fold increase in ALP indicate?

A

Hepatocellular injury

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6
Q

What does a < 10 fold increase in ALT and a > 3 fold increase in ALP indicate?

A

Cholestasis

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7
Q

When should Gamma GT be reviewed?

A

When there is a rise in ALP

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8
Q

What does an increase in Gamma GT indicate?

A

Biliary epithelial damage and bile flow obstruction.

Can also be raised in response to alcohol and drugs

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9
Q

What does a markedly raised ALP and GGT indicate?

A

Cholestasis

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10
Q

What does an isolated ALP increase indicate?

A

non-hepatobiliary pathology. Bone breakdown will raise ALP levels:

  • bony metastasis or primary bone tumours
  • vitamin D deficiency
  • recent bone fractures
  • renal osteodystrophy
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11
Q

What does an isolated rise in bilirubin indicate?

A

Pre-hepatic jaundice, usually caused by Gilbert’s syndrome or haemolysis

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12
Q

What should be done if haemolysis is suspected?

A

Check blood film, FBC, reticulocyte count, haptoglobin and LDH

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13
Q

Name some of the liver’s synthetic functions?

A

Conjugation and elimination of bilirubin
Synthesis of albumin
Synthesis of clotting factors
Gluconeogenesis

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14
Q

What investigations assess synthetic liver function?

A

Serum bilirubin
Serum albumin
Prothrombin time
Serum blood glucose

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15
Q

What is bilirubin?

A

A breakdown product of haemoglobin

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16
Q

Where is bilirubin conjugated?

A

The liver

17
Q

How does conjugated hyperbilirubinaemia affect urine?

A

It is water soluble so will pass into urine as urobilinogen = darker urine

18
Q

How does unconjugated hyperbilirubinaemia affect urine?

A

It is not water soluble so will not affect the colour of urine

19
Q

When may stools be able to differentiate between the causes of jaundice?

A

Can determine if jaundice is post-hepatic jaundice as blockage = bile and pancreatic lipase unable to reach bowel = steatorrhoea

20
Q

Normal urine + normal stools

A

Pre-hepatic cause of jaundice

21
Q

Dark urine + normal stools

A

Hepatic cause of jaundice

22
Q

Dark urine + pale stools

A

Post hepatic cause

23
Q

Name some causes of unconjugated hyperbilirubinaemia?

A

Haemolysis (haemolytic anaemia)
Impaired hepatic uptake (drugs, congestive heart failure)
Impaired conjugation (gilbert’s syndrome)

24
Q

Name some causes of conjugated hyperbilirubinaemia ?

A

Hepatocellular injury
Cholestasis
Rotor’s syndrome
Dubin-Johnson Syndrome

25
Q

What is the function of albumin?

A

Synthesised in the liver and helps to bind water, cations, fatty ions and bilirubin. It also plays a key role in maintaining oncotic pressure of blood.

26
Q

Why might albumin levels fall?

A

Liver disease = decreased production of albumin

Inflammation triggering an acute phase response which temporarily decreases albumin production

Excessive loss of albumin due to protein-losing enteropathies or nephrotic syndrome

27
Q

What is prothrombin time?

A

A measure of the bloods coagulation tendency. Assesses the extrinsic pathways

28
Q

Name some secondary causes that may increase PT?

A

Anticoagulants and Vit K deficiency

29
Q

Why can PT be increased in hepatic pathology?

A

Because the liver is responsible for clotting factor synthesis

30
Q

What happens when ALT>AST ?

A

Chronic liver disease

31
Q

What happens when AST>ALT?

A

Cirrhosis

Acute alcoholic hepatitis

32
Q

What are the causes of acute hepatocellular injury?

A

Poisoning (paracetamol overdose)
Infection (hep A and B)
Liver ischaemia

33
Q

Causes of chronic hepatocellular injury?

A

Alcoholic fatty liver disease
NAFLD
Chronic infection (hep B or C)
Primary billiary cirrhosis

34
Q

What are some uncommon causes of chronic hepatocellular injury?

A

Alpha-1 antitrypsin deficiency
Wilson’s disease
Haemochromatosis

Data Interpretation (2 decks)

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