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MELS301 > Liver Function > Flashcards

Liver Function Flashcards

1
Q

What are the components of the portal triad?

A

Portal vein, portal artery and bile duct.

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2
Q

How does blood flow occur in the lobules of the liver?

A

Blood comes from the portal vein and arteries and flows down the sinusoids of the lobe to the central vein in which it drains.

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3
Q

How does necrosis spread in the liver?

A

From the central vein outwards because it is the most hypoxic area.

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4
Q

What are the 7 functions of the liver?

A 
Carbohydrate metabolism
Fat metabolism
Protein metabolism
Hormone metabolism
Drugs and toxins metabolism and excretion
Storage
Bilirubin metabolism and excretion
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5
Q

What are the 4 most common liver disorders?

A

Hepatitis
Cirrhosis
Cholestasis
Tumours

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6
Q

What is hepatitis?

A

Inflammation of hepatocytes can be acute or chronic.

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7
Q

What is cirrhosis?

A

End stage liver disease with fibrosis of liver tissue.

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8
Q

What is cholestasis?

A

Obstruction of bile flow intra or extra-hepatic.

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9
Q

What is bilirubin?

A

A yellow pigment present in bile, urine and faeces. It is a water insoluble breakdown product of normal haem catabolism 80% from Hb and 20% from myoglobin and cytochromes.

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10
Q

What is ligandin?

A

A carrier protein in the membrane of hepatocytes for bilirubin.

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11
Q

Where is bilirubin conjugated?

A

The smooth endoplasmic reticulum of hepatocytes.

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12
Q

What is unconjugated bilirubin?

A

Indirect bilirubin, the first stage from opening the haem ring. It is not soluble in water so is bound to albumin and transported to the liver.

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13
Q

How is unconjugated (indirect) bilirubin measured?

A

Not directly. Conjugated bilirubin is subtracted from total bilirubin.

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14
Q

What is conjugated bilirubin?

A

Direct bilirubin. Water soluble and readily transported to bile, it is excreted in bile through the bile duct into the small intestine to help with food digestion.

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15
Q

How do you measure total bilirubin?

A

Diazo reaction

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16
Q

How does the Diazo reaction work for total bilirubin?

A

It uses an aqueous solution with an accelerator (caffeine) this displaces the albumin from the unconjugated bilirubin making the bilirubin water soluble by forming hydrogen bonds with the caffeine. It then reacts with the diazo reagent to form azobilirubin which is measured spectrophotometrically.

17
Q

What absorbance is azobilirubin measured at?

A

598nm.

18
Q

How does the diazo reaction measure direct bilirubin?

A

The diazo reaction is used but without an accelerator and it is performed at pH 1.0 to prevent any unconjugated bilirubin from reacting. Azobilirubin is then measured spectrophotometrically.

19
Q

What are some sample considerations to make when measuring bilirubin with a photometric test?

A

There is potential interference with lipaemia which is a problem in patients with liver problems.
In-vitro haemolysis.

20
Q

How is bilirubin light sensitive?

A

Light at 450nm disrupts the intramolecular hydrogen bonds creating water soluble isomers so is important that it is light protected otherwise you get a falsely low result.

21
Q

How can you detect urine urobilinogen?

A

It reacts with Ehrlic’s reagent to give a pink-red colour.

22
Q

What is jaundice?

A

It occurs when bilirubin concentration increases in serum and tissues, the patient turns yellow and may have puritis which is itchiness.

23
Q

What is pre-hepatic jaundice?

A

Jaundice which occurs as a result of excess bilirubin arriving at the liver for example due to haemolysis. You get unconjugated hyperbilirubinaemia which is bound to albumin as not water soluble so does not end up in the urine.

24
Q

What is hepatic jaundice?

A

This is the most common form of jaundice caused by hepatocellular damage such as hepatitis. You get impaired hepatocellular uptake, defective conjugation or abnormal secretion. This leads to both unconjugated and conjugated hyperbilirubinaemia so there may be bilirubin in the urine.

25
Q

What is post-hepatic jaundice?

A

Mechanical obstruction of bile flow in the intestine causes by gallstones or a tumour. Causes conjugated hyperbilirubinaemia and bilirubin in the urine. You get decreased urobilinogen and the stool loses pigmentation.

26
Q

What tests are used to measure hepatocellular integrity?

A

AST and ALT

27
Q

What tests are used to measure biliary excretion function?

A

Bilirubin, urine bilirubin and urobilinogen, ALP and GGT.

28
Q

What tests are used to measure hepatocellular function?

A

Proteins are secreted into the blood so measure serum albumin, PT, and APTT.

29
Q

What causes acute hepatitis?

A

Usually viruses such as HAV, HBV, HCV, HDV, HEV, EBV and CMV. Also drugs, toxins and may be autoimmune.

30
Q

How long does acute hepatitis last?

A

10-12 weeks normally, it is self limiting.

31
Q

How long does chronic hepatitis last?

A

Longer than 6 months is classified as chronic.

32
Q

What causes chronic hepatitis?

A

HBV, HCV, alcohol or autoimmune hepatitis.

33
Q

What test results would you expect from chronic hepatitis?

A

AST and ALT would be high but other liver functions should be normal as nothing to do with cholestasis.

34
Q

What test results would you expect from acute hepatitis?

A

Increased AST and ALT in the pre-icteric phase and then also increased ALP in the icteric phase as there is biliary obstruction.

35
Q

What are the symptoms of cholestasis?

A

Jaundice, pruritus, xanthomas, intestinal malabsorption which causes deficiencies in fat soluble vitamins (ADK)

36
Q

What is the treatment of cholestasis?

A

Removal of the obstruction if possible. If it does not get treated it may lead to gradual destruction of hepatic bile ducts (biliary cirrhosis)

37
Q

What is intra-hepatic cholestasis?

A

Where the obstruction of the bile duct leads to build up of bile in hepatocytes.

38
Q

What is extra-hepatic cholestasis?

A

Obstruction of the common bile duct caused by gallstones (cholelithiasis), infection, pancreatic disease or tumours.

39
Q

What are the 2 main types of gallstones?

A

Cholesterol gallstones which are made of crystalline cholesterol monohydrate.
Pigment stones which are made of bilirubin calcium salts.

MELS301 (10 decks)

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