Liver Function Tests

Question 1

What is the current weekly recommended alcohol allowance for men and women? Why has it been lowered?

Answer 1

14 units per week, lowered because of newly learned link between alcohol consumption and cancer (not just between alcohol consumption and liver damage)

Question 2

What is cholestasis and how does it present?

Answer 2

Blockage/reduction in bile flow, results in dark urine (lots of urobilinogen excreted) and pale stool (can’t excrete stercobilinogen)

Question 3

What does an increased number of spider naevi above the nipple line indicate?

Answer 3

Alcoholic liver disease

Question 4

Why is the liver a common site of metastasis?

Answer 4

Lots of blood flow here, so often metastases travel via blood and end up here

Question 5

What do raised ALT and AST indicate?

Answer 5

Hepatocellular damage

Question 6

What do raised ALP and GGT indicate?

Answer 6

Obstruction

Question 7

Where does bilirubin come from?

Answer 7

Produced from the breakdown of RBCs

Question 8

What are the products of the breakdown of RBCs and what happens to each of them?

Answer 8

Iron (re-used), globin (re-used), biliverdin (reduced to bilirubin)

Question 9

What is biliverdin formed from? What is it reduced to?

Answer 9

Biliverdin (green) is formed from haem. It is reduced to form bilirubin.

Question 10

Name three conditions which increase bilirubin levels

Answer 10

Cholestasis (biliary obstruction), hepatocellular damage, haemolysis

Question 11

What is ‘conjugated bilirubin’? Where is bilirubin conjugated?

Answer 11

Bilirubin with glucuronic acid (bilirubin glucuronate), conjugated in the liver

Question 12

What is the solubility of conjugated and unconjugated bilirubin?

Answer 12

Conjugated bilirubin is soluble in water, unconjugated bilirubin is insoluble

Question 13

Why is it important that conjugated bilirubin is water soluble?

Answer 13

So it can be excreted into the duodenum as bile

Question 14

Why does liver damage increase bilirubin levels? What condition does this lead to?

Answer 14

Liver damage means that bilirubin can’t be conjugated with glucuronic acid, so it can’t be excreted (because insoluble) so builds up- Leads to jaundice

Question 15

Where is soluble bilirubin excreted? In what forms is bilirubin excreted in urine and stool?

Answer 15

. Excreted from liver through bile duct into duodenum

. Stercobilin in stools, urobilin in urine

Question 16

Some bilirubin enters enterohepatic recycling. What does this involve?

Answer 16

Bilirubin/bile salts/urobilinogen are send back to the liver to be re-used, so lots of new bile salts don’t have to be synthesised from scratch

Question 17

How do pale stools indicate liver dysfunction?

Answer 17

. Liver not working so can’t conjugate bilirubin

. Bilirubin glucuronate not converted to stercobilin, which normally colours stool brown

Question 18

What does dark stool indicate with regards to the liver?

Answer 18

Shows too much bilirubin in blood, likely from cholestasis (bile duct blocked so bilirubin can’t be excreted into duodenum, builds up), hepatocellular damage (unconjugated bilirubin can’t be excreted, builds up), haemolysis (RBCs broken down to produce excess bilirubin)

Question 19

What is the half-life of albumin? Why is this significant when using albumin as a marker for liver damage?

Answer 19

16-24 days- Quite long half-life, so low albumin is a marker of long term liver damage (liver normally synthesised albumin and clotting factors)

Question 20

How can low albumin contribute to ascites?

Answer 20

Low albumin causes a decrease in oncotic pressure in the blood, so fluid leaks from interstitial spaces into the peritoneal cavity instead

Question 21

How come low levels of clotting factors can show acute/chronic liver damage, whereas low albumin indicates long term/chronic damage?

Answer 21

Clotting factors have a short half life, so can’t really differentiate acute/chronic damage. Albumin has a longer half life, so low albumin indicates more chronic long-term damage

Question 22

Why does jaundice present with pruritus?

Answer 22

Excess bilirubin is toxic, which presents as itching of the skin

Question 23

What is prehepatic jaundice? What is it often caused by? (Give 2)

Answer 23

. Unconjugated bilirubin produced faster than liver can conjugate it for excretion, so there’s a backlog build up of bilirubin in the blood
. Often caused by haemolytic anaemias e.g. spherocytosis (Lots of RBCs broken down produces excess bilirubin) or Gilbert’s syndrome (reduced levels of UDP-glucuronosyl transferase, which normally conjugates bilirubin)

Question 24

What is hepatocellular jaundice? How is this usually detected? What symptoms often present?

Answer 24

. Hepatocellular damage so can’t conjugate bilirubin to bilirubin glucuronate, so there’s reduced excretion of bilirubin (=build up in blood)
. Detected by elevated ALT and AST (transaminases) in blood
. Normal/pale stools (stercobilin not excreted due to lack of soluble bilirubin)

Question 25

What is the physiology behind pale stools?

Answer 25

If there’s a lack of bilirubin glucuronate (soluble bilirubin), it means less stercobilin can be produced to colour stool brown

Question 26

What can you prescribe to relieve symptoms jaundice, pruritus, and nausea? What does this drug do?

Answer 26

. Cholestyramine
. Binds to bile (and thus bilirubin/bile salts) and prevents them being recycled and reabsorbed, causing bilirubin to be excreted
. Reduces toxic levels of bilirubin to relieve symptoms

Question 27

How can liver cirrhosis lead to ascites?

Answer 27

Liver cirrhosis can cause decrease in BP, so lots of aldosterone is produced to counteract this (secondary hyperaldosteronism). This causes sodium retention, which can then draw fluid into the abdominal cavity (=ascites)

Question 28

How can liver dysfunction lead to encephalopathy? How would you treat this?

Answer 28

Gut flora produce many nitrous products (e.g. ammonia) which are normally cleared by the liver but can be toxic in higher amounts
Prescribe neomycin, metronidazole, and lactulose

Question 29

Why is gastric bleeding of particular concern in those with liver disease?

Answer 29

Damaged liver doesn’t produce sufficient clotting factors to deal with a gastric bleed, so could be excessive gastric bleeding

Question 30

How can you decrease the risk of bleeding oesophageal varices?

Answer 30

Prescribe beta-blockers to decrease BP

Question 31

What is the main test for liver fibrosis?

Answer 31

Fibroscan (Transient Elastography, TE)