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Liver diseases > Diagnosis and Monitoring > Flashcards

Diagnosis and Monitoring Flashcards

1
Q

What are the four overriding processes to diagnosing liver disease?

A

Medical history and recording the signs and symptoms
Blood tests
Imaging
Liver biopsy

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2
Q

What are the blood tests are used in the diagnosis of liver disease?

A

Liver function tests
Full blood count
Electrolytes
Viral screens
Prothrombin/clotting

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3
Q

What happens to FBC in end stage liver disease?

A

Bone marrow suppression, with low red, white blood cells and platelets

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4
Q

Why are viral screens taken in blood tests?

A

In order to determine whether a virus is the cause of liver disease (e.g. Hepatitis).

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5
Q

What types of imaging is used to diagnose liver disease?

A

Imaging is used to detect the functionality and the structure of organs related to the liver. This can include:
Ultrasound
CT
MRI

This can include screening organs such as the gall bladder, liver and bile ducts

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6
Q

How is a liver biopsy carried out?

A

Under local anaesthetic a long thin needle is inserted through the chest wall to sample a piece of liver tissue, specifically between the lower ribs on the right hand side of the body.

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7
Q

State the serum enzyme liver function tests.

A

Aspartate transaminase
Alanine transaminase
Gamma Glutamyl transferase
Alkaline phosphatase

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8
Q

What is the enzyme aspartate transaminase responsible for?

A

It is responsible for catalysing the reversible conversion of aspartate and alpha ketoglutarate to oxaloacetate and glutamate. Therefore is involved in gluconeogenesis.

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9
Q

Where is the enzyme aspartate transaminase found in the body?

A

Hepatocytes in addition to the heart, brain and skeletal muscle.
Therefore interpretation of these blood test results should not be considered in isolation when diagnosing or monitoring liver disease.

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10
Q

What is the reference range of aspartate transaminase (AST)?

A

5-40IU/L

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11
Q

What is the enzyme alanine transaminase responsible for?

A

Catalysing the reversible transfer of an amino acid for L-alanine to alpha ketoglutarate resulting in pyruvate and L-glutamate.

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12
Q

Where is the enzyme alanine transaminase found in the body?

A

Mainly in the liver, much more specific to hepatocytes in comparison to aspartate transaminase.

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13
Q

Explain elevations of ALT and AST.

A

Very high levels: In acute vital/toxic hepatitis

High levels: Cholestatic jaundice/cirrhosis

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14
Q

Are rises in AST and ALT proportional to extent of severity?

A

Yes the degree of rise in ALT and AST is proportional to the severity/ extent of hepatic damage

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15
Q

When is the AST/ALT useful in the diagnosis of liver disease?

A

It is crucial for differentiating the type of liver disease.
AST/ALT ratio of 2 or greater indicates alcohol induced hepatic injury whereas for most other types of liver disease the AST/ALT ratio is less than or equal to 1.

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16
Q

What is the enzyme Gamma glutamyl transferase responsible for?

A

Catalyses the transfer of gamma glutamyl moiety of glutathione to an amino acid, peptide and water, meaning it is responsible for the formation of glutamate.

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17
Q

What is the reference range for Gamma Glutamyl transferase (GGT)?

A

5-45 IU/L

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18
Q

Where is the enzyme GGT found?

A

Hepatocytes in addition to the kidneys, pancreas and prostate

19
Q

Explain elevations in GGT.

A

Very high levels: biliary obstruction
Lower increased levels: chronic alcohol/drug toxicity, hepatitis, cirrhosis or cholestasis

Elevations may also be caused by disorders the other organs the enzyme is found in.

20
Q

When do levels of GGT drop according to alcohol use?

A

GGT levels drop 3-6 weeks of alcohol abstinence

21
Q

What is the enzyme alkaline phosphatase responsible for?

A

Removal of the phosphate group from nucleotides, proteins and alkaloids

22
Q

What is the reference range for alkaline phosphatase?

A

20-100 IU/L

23
Q

Where is the enzyme alkaline phosphatase found?

A

Bone, intestinal wall, renal tubules, placenta

24
Q

Explain elevations in alkaline phosphatase.

A

Very high levels found in: biliary obstruction

Elevations may also be caused by disorders the other organs the enzyme is found in.

25
Q

What is the reference range of bilirubin?

A

0-17 micromol/L

26
Q

When does jaundice occur in relation to the raise in bilirubin levels?

A

Jaundice occurs when the bilirubin level is elevated above >35 micromol/L with the rise reflecting jaundice depth.

27
Q

What does measuring bilirubin achieve?

A

It is good for monitoring disease progression

28
Q

Describe the pathophysiology of both conjugated and unconjugated bilirubin.

A

When red blood cells are broken down haemoglobin is released which is then converted in the blood to unconjugated bilirubin. Unconjugated bilirubin becomes bound to plasma albumin where it is transported to the liver where it becomes conjugated to glucoronate to become excreted in the bile.

29
Q

In reference to the pathophysiology of bilirubin, what is the purpose of measuring both conjugated and unconjugated bilirubin?

A

By interpretating both types of bilirubin results it is possible to differentiate between the cause of any noticeable changes in bilirubin levels.
Elevations in unconjugated bilirubin is associated with excessive red blood cell breakdown
Whereas elevations in conjugated bilirubin is likely due to a type of liver problem due to the inability to excrete conjugated bilirubin resulting in accumulation.

30
Q

What are the reference ranges for total protein and albumin?

A

Total protein: 60-80 g/dL
Albumin: 35-50 g/dL

31
Q

Where is albumin synthesised?

A

Solely by the liver as a type of plasma protein, therefore in liver impairment you would likely see an reduced albumin level due to the inability of hepatocytes to synthesis the protein.

32
Q

What is the half life of plasma albumin and what considerations should you make?

A

Plasma half life of albumin is: 20-26 days

Therefore any reductions in albumin indicate long term liver damage due to the long half life of the protein.

33
Q

When does oedema occur according to albumin levels?

A

<20 g/dL causing fluid overload due to changes in the oncotic pressure.

34
Q

What is prothrombin time?

A

The average time taken for the blood to clot. A number lower than the reference range means that the blood clots more quickly than normal (at risk of thrombus), a number higher than the reference range means that it takes longer than normal for the blood to clot (at risk of a bleed).

35
Q

What is the reference range prothrombin time?

A

Sources can vary but usually between about 10-15 seconds.

36
Q

What happens to prothrombin time when hepatocellular damage and cholestasis occurs?

A

Hepatocytes are responsible for producing certain clotting factors, specifically Factors 2, 7 and 9* and 10. Therefore when hepatocellular damage occurs, the hepatocytes loose their ability to produce these clotting factors and hence prothrombin time is increased.

Cholestasis is defined as a decrease in bile flow due to impaired secretion by hepatocytes or to obstruction of bile flow through intra-or extrahepatic bile ducts. This means that bile salts are unable to be excreted from the bile ducts. Bile salts are essential for Vitamin K intestinal absorption which is required to produce the Vitamin K-dependent clotting factors 2, 7, 9 and 10. Therefore is cholestasis prothrombin time is also increased.

37
Q

What is the method of differentiating between hepatocellular damage and cholestasis as the cause of an increased prothrombin time?

A

Administration of Vitamin K 10mg for 3 days, as in cholestasis prothrombin time will decrease as the hepatocytes are responsive and can produce clotting factors once more.

However if increase prolonged time is as a result of hepatocellular damage there will be no improvement in prothrombin time due to hepatocytes remaining unresponsive to even increased levels of Vitamin K, and not able to produce the clotting factors.

38
Q

What is the reference range for urea?

A

2.5-7.8 mmol/L

39
Q

What is the reference range for ammonia?

A

16-60 micromol/L in males and 11-51 micromol/L in females

40
Q

How do urea and ammonia levels change in liver disease?

A

In liver disease, the inability of hepatocytes to convert ammonia to urea, leads to accumulation of ammonia (increased levels) and decreased urea levels.
Increased ammonia levels puts the patient at risk of hepatic encephalopathy.

41
Q

Which tests would you use to decide whether the liver is working?

A

Albumin and clotting factors, as hepatocytes within the liver are responsible for the synthesis of the plasma protein and clotting factor.

42
Q

Which tests would you use to decide whether the liver is damaged?

A

ALT
AST
GGT
ALT/AST ratio

43
Q

Which tests would you use to decide whether the liver is secreting?

A

Bilirubin
ALP
GGT

Liver diseases (6 decks)

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