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Gastrointestinal > Liver Function Tests > Flashcards

Liver Function Tests Flashcards

1
Q

What enzymes are tested for in a liver function test?

A

(ALT/AST) - serum transaminases
(ALP) - Alkaline Phosphatase
(GGT) - gamma glutamyl transpeptidase

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2
Q

What are the substances which are indications of the intrinsic synthetic function?

A

albumin
prothrombin time/INR
bilirubin

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3
Q

What are transamines?

A

Hepatic enzymes that are usually intracellular, but are released from hepatocytes in context of hepatocellular injury.

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4
Q

What reaction do transamonases catalyse?

A

y-amino group transfer e.g. aspartate or alanine to ketoglutarate

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5
Q

Give an example of an ALT and it’s properties

A

alanineamino transferase

  • more sensitive than AST
  • predominantly cytosol-located
  • found mainly in the liver
  • half life 47hrs
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6
Q

Give an example of an AST and its properties

A

aspartate aminotransferase

  • in cytosol and mitochondria
  • found in Liver, Heart, Pancreas, Skeletal muscle, Brain, Lungs, RBCs, WBCs
  • Half Life Circa 17hrs
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7
Q

What can be learned from aminotransferase levels?

A
  • deranged in most aetiologies
  • increase in hepatocellular pathologies
  • sometimes levels effect level of damage
  • obstructive jaundice usually less than 500U/L
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8
Q

What are alkaline phosphatases?

A

Enzymes that catalyzes the hydrolyses of a number of organic phosphate esters.
Half-life about 1 week; therefore often lag to rise and slow precipitation in resolution of pathology.

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9
Q

What is the indication of biliary cholestasis (decrease in bile flow due to obstruction or decreased secretion)?

A

High ALP

high alkaline phophatase

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10
Q

Where does alkaline phosphatase ALP originate from?

A 
epithelial cells of the biliary tree ducts
bone 
placenta
intestine
kidney
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11
Q

What is gamma glutamyl transpeptidase?

A

Enzyme involved in gluthionine metabolism, transfer of amino acids across cellular membranes and leukotriene metabolism

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12
Q

Why are GGTs useful when compared to ALPs?

A

they help determine whether the elevated ALPs are due to bone or liver damage

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13
Q

Where do GGTs originate?

A 
liver
kidneys
bile duct
pancreas
gallbladder
spleen
heart
brain
seminal vesicle
Not bone.
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14
Q

What is GGT used as a marker for?

A

liver or cholestatic disease

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15
Q

What can induce GGT elevation?

A 
drugs particularly anticonvulsants and TCAs and Paracetamol. 
Diabetes mellitus
pancreatic disease
COPD
renal disease
alcohol consumption
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16
Q

What is the normal process for bilirubin?

A

Predominantly a breakdown product of Heme
Transported to liver bound to albumin
Uptake into the hepatocytes
Undergoes conjugation
Excreted via urine/faeces (Urobilinogen/Stercobilinogen)

17
Q

What are 2 forms that bilirubin can be found in in blood tests?

A

conjugated and unconjugated

18
Q

What clotting factors is the liver responsible for the synthesis of?

A

Factors 1,2,5,7,9,12,13

1 (fibrinogen) and 2 (prothrombin)

19
Q

What does the PT measure?

A

conversion time from prothrombin to thrombin

20
Q

What is elevated PT an indication of?

A 
reduced synthetic functionality
can also be a result of
Drugs (inc Warfarin)
Bile malabsorption causing relative Vit K deficiency
Consumptive coagulopathies
Congenital coagulopathy
21
Q

What is one of the most important aspects of LFT history takings?

A

what has changed since the difference in measures - any and all medications

22
Q

What LFT indicates hepatocellular injury?

A

ALT/AST> ALP

raised bilirubin

23
Q

What LFT indicates cholestasis?

A

ALP>ALT/AST

raised bilirubin

24
Q

What LFT indicates Prolonged Jaundice/Vit K, Malabsorption

& Hepatocellular Dysfunction?

A

Increased PT/INR

25
Q

What is the problem with the albumin test?

A

It is a difficult measure of liver function when used in isolation

26
Q

What is the normal AST:ALT ratio?

A
  1. 8, >2 suggests alcohol

- can give a picture of the hepatocellular picture

27
Q

What diseases can cause a strange AST:ALT ratio so need to be ruled out?

A 
Coeliac Disease
Muscle disorders (Myositis, Rhabdomyolysis)
Creatine Kinase (CK)
Adrenal Insufficiency
Anorexia Nervosa
Thyroid Disorders
28
Q

What causes an increase in unconjugated bilirubin?

A

Increased bilirubin production
Impaired hepatic bilirubin uptake
Impaired bilirubin conjugation

29
Q

What can cause increased bilirubin production?

A

Extra/intravascular haemolysis

Extravasation of blood into tissues

30
Q

What can cause impaired hepatic bilirubin uptake?

A

Heart Failure
Portosystemic Shunts
Drugs; Rifampicin, Probenecid

31
Q

What can cause impaired bilirubin conjugation?

A

Gilbert’s/CN Type II
Hyperthyroidism
Advanced Liver Disease

32
Q

What can cause an increase in conjugated bilirubin?

A

Extrahepatic Cholestasis (Biliary Obstruction)
Intrahepatic Cholestasis
Drugs

33
Q

What drugs can cause an increase in conjugated bilirubin?

A

Alkylated Steroids

Chlorpromazine, herbs, Rifampicin

34
Q

What can cause Extrahepatic Cholestasis (Biliary Obstruction)?

A 
Cholelithiasis
Primary Sclerosisng Cholangitis
Cholangiocarcinoma
Head of Pancreatic Tumour
Acute/Chronic Pancreatitis
35
Q

What can cause Intrahepatic Cholestasis?

A 
Sepsis/Hypoperfusion states
Cirrhosis
Infiltrative Diseases
TPN
Acute Hepatitis

Gastrointestinal (12 decks)

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