Liver Function Tests Flashcards

1
Q

What is the largest solid organ in the body, weighing around 1.5 kg?

A
  • The liver
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2
Q

Where is the liver located in the body?

A
  • In the right hypochondrium, extending to the epigastrium.
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3
Q

Which structure effectively divides the liver into a right and left lobe?

A
  • The falciform ligament
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4
Q

How many blood supplies does the liver receive, and what are they?

A
  • 2 blood supplies
  • the hepatic portal vein,
  • the hepatic artery
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5
Q

What is the function of the hepatic portal vein in liver perfusion ?

A
  • It carries blood from the intestine before distribution to the general circulation.
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6
Q

What is the role of the hepatic artery in liver perfusion?

A
  • It supplies the liver with oxygen and nutrients.
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7
Q

What are the 7 primary physiological functions of the liver?

A
  1. Detoxification
    1. Glucose homeostasis
    2. Lipid homeostasis
    3. Protein synthesis and metabolism
    4. Bile acid metabolism and transport
    5. Hormone regulation
    6. Immunological function
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8
Q

How does the liver detoxify drugs?

A
  • occurs via cytochrome P450 enzymes
  • in a two-stage process involving oxidation and conjugation reactions.
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9
Q

What role does the liver play in glucose homeostasis?

A
  • The liver regulates blood glucose levels by storing and releasing glucose as needed.
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10
Q

How is the liver involved in lipid homeostasis?

A
  • liver synthesizes, stores, and metabolizes lipids, including cholesterol and triglycerides.
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11
Q

What proteins are synthesized and metabolized by the liver?

A
  • liver synthesizes, stores, and metabolizes lipids, including cholesterol and triglycerides.
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12
Q

How does the liver regulate hormones?

A
  • It conjugates oestrogen.
    • It metabolizes and regulates thyroxine (T4).
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13
Q

What immunological function does the liver perform?

A
  • The liver helps protect the body by filtering blood and producing immune-related proteins.
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14
Q

Can liver function tests (LFTs) be used in isolation?

A
  • No, LFTs should be used in context.
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15
Q

Name the standard parameters included in liver function tests (7)

A
  1. Alkaline phosphatase (AP)
    1. Alanine aminotransferase (ALT)
    2. Aspartate aminotransferase (AST)
    3. Gamma-glutamyl transferase (GGT)
    4. Bilirubin
    5. Albumin
    6. Total protein
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16
Q

Which parameter is not officially an LFT but is still useful in assessing liver function?

A
  • Clotting screen
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17
Q

What are the soluble cytoplasmic enzymes?

A
  • AST & ALT
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18
Q

What are the membrane - associated enzymes ?

A
  • AP & GGT
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19
Q

What does Alkaline Phosphatase (AP) refer to ?

A
  • A widely distributed set of isoenzymes.
20
Q

Where is hepatic AP produced, and when is its production increased?

A
  • Hepatic AP is produced by hepatocytes
  • its production increases with damage to the biliary system.
21
Q

What 3 conditions can cause increased levels of Alkaline Phosphatase (ALP)?

A
  • Cholestasis - obstruction to normal movement within the biliary system
  • Bone disease – Paget’s disease, bone malignancy, growth in teenagers
  • Pregnancy – elevated at the end of pregnancy and beyond, especially with breastfeeding.
22
Q

What are the two key aminotransferases measured in liver function tests?

A
  • Aspartate aminotransferase (AST).
  • Alanine aminotransferase (ALT).
23
Q

Where is AST widely distributed in the body?

A
  • Liver, heart, pancreas, lung, RBCs, and skeletal muscle.
24
Q

How do AST and ALT typically behave during liver injury ?

A
  • They tend to rise and fall in unison and are often discussed together.
25
What do increased serum levels of aminotransferases indicate?
- Hepatocellular damage or inflammation
26
Where are high concentrations of GGT found in the body?
- Liver, kidneys, pancreas, intestine, and prostate.
27
What does elevated GGT indicate when raised alongside Alkaline Phosphatase (AP)?
- Hepatobiliary disease
28
In which conditions is GGT often elevated?
- Alcoholic liver disease (ALD). - As a result of certain adverse drug reactions (ADRs).
29
Why is albumin a useful measure of hepatic functional capacity?
- most albumin is manufactured in the liver, making it a good indicator of liver function.
30
What is the half-life of albumin, and what does it signify?
- Around 20 days, reflecting a relatively long-term picture of disease.
31
By how much can albumin levels decrease in cirrhotic patients?
- Up to 50%
32
Why is albumin important in terms of drug binding?
- most acidic drugs are strongly bound to albumin
33
In which conditions can albumin levels also be altered?
1. Crohn’s disease. 2. Malnutrition. 3. Malignancy. 4. Nephrotic syndrome.
34
Which plasma proteins are most significant in liver function?
- Albumin and clotting factors
35
Name some additional plasma proteins produced by the liver ( don't need to know in detail )
1. Alpha-fetoprotein 2. Gamma-globulins 3. Transferrin 4. Ferritin 5. α1-antitrypsin
36
What does INR stand for, and what is its significance?
- International Normalized Ratio - it measures blood clotting, indicating liver function related to clotting factor production.
37
What is considered an abnormal INR?
- An INR greater than 1.3
38
How is INR affected in patients with liver disease?
- Patients with chronic or acute liver disease may have elevated INRs due to impaired clotting factor production.
39
How can INR be used in the context of paracetamol poisoning?
- It can serve as a marker of hepatocellular damage.
40
3 main causes of jaundice based on bilirubin metabolism ?
- increased production of bilirubin / decreased uptake (pre-hepatic) - decreased metabolism (intra-hepatic) - decreased excretion (hepatic + extra-hepatic)
41
What conditions are associated with unconjugated hyperbilirubinaemia ?
- Haemolysis • Gilberts syndrome • Crigler-Najjar syndrome • Drugs e.g. rifampicin
42
What conditions are associated with conjugated hyperbilirubinaemia ?
- Intra or extra-hepatic cholestasis • Acute Hepatitis • Cirrhosis
43
Stages of Bilirubin metabolism
- unconjugated bilirubin binds to albumin in blood - dissociates from albumin in the hepatic sinusoid, it is taken up by hepatocytes - unconjugated bilirubin conjugated with glucuronic acid by UDP-glucuronosyltransferase to conjugated bilirubin - conjugated bilirubin converted to urobilinogen in the small intestine by bacterial proteases - 10% of urobilinogen reabsorbed into hepatocyte via hepatic portal vein - 90% in feces
44
What is the significance of raised ALP and GGT in liver function tests?
- ALP raised solely consider bone-related causes such as: vitamin D deficiency - ALP + GGT raised: indicates cholestasis (biliary obstruction or dysfunction)
45
What does greater than10x increase in ALT + less than 3x increase in ALP indicate?
- hepatocellular injury, such as acute hepatitis or liver cell damage
46
What does less than 10x increase in ALT + greater than 3x increase in ALP indicate ?
- cholestasis
47
What does a sole increase in ALP suggest?
- bone pathology