Bile and jaundice

Question 1

What is bile?

Answer 1

• A brownish-yellow or green fluid that is secreted by liver and stored in gallbladder.

Question 2

What are the functions of bile?

Answer 2

• Excretory
• Digestive

Question 3

Discuss the excretory function of bile.

Answer 3

• Exogenous and endogenous products can accumulate in bile and be excreted.

Question 4

What are the names of the macrophages of the liver?

Answer 4

• Kupffer cells: maintain liver function.

Question 5

Discuss the digestive function of bile.

Answer 5

• Associated mainly with fats.
• Increases pH to neutralise acidity of gastric content. Alkaline secretion.
• Bile salts and phospholipids emulsify fats into smaller droplets.
• Bile salts activate pancreatic hydrolyse precursors.

Question 6

Where do we get bile acids and salts from?

Answer 6

• Come from breakdown of cholesterol.

Question 7

Name 2 primary bile acids (Liver).

Answer 7

• Cholic acid
• Chenodeoxycholic acid.

Question 8

Name 2 secondary bile acids (Gut).

Answer 8

• Deoxycholic acid
• Lithocholic acid

Question 9

What is bilirubin?

Answer 9

• A natural degradation product of haem in erythrocytes.

Question 10

What processes need to happen for production of bilirubin?

Answer 10

• Phagocytosis and/or lysis of RBCs.

Question 11

Describe extra-vascular formation of bilirubin.

Answer 11

1. RBC undergoes phagocytosis and/or lysis.
2. Haemoglobin is released and broken into Haem and Globin.
3. Globin is further degraded into AAs.
4. Haem is broken into Fe2+ and a product of its breakdown is bilirubin.

Question 12

Discuss haem degradation and processing.

Answer 12

1. Haem is degraded into bilirubin.
2. Bilirubin binds to albumin and is transported in bloodstream.
3. Then taken up by liver.
4. It is then conjugated with glucuronic acid to make it water soluble.
5. It is then excreted into bile.
6. Urobilinogens then form in intestinal tract.
   - Can either be re-absorbed and excreted from kidney as urinary urobilin, or excreted as faecal stercobilin

Question 13

How exactly is haem degraded into bilirubin?

Answer 13

• Via 2 enzymes:
  1. Haem oxygenate
  2. Biliverdin reductase
• Haem–biliverdin—unconjugated bilirubin

Question 14

Discuss the metabolism of bilirubin.

Answer 14

1. Haem is degraded and produces bilirubin.
2. Bilirubin binds to albumin, transported into bloodstream then is taken up by liver.
3. In the liver, binds to cytoplasmic proteins: ligand + protein Y.
4. Then conjugated with glucoronic acid is catalysed by UDP-glucuronyl transferase to make it water soluble.
5. Conjugated bilirubin is secreted into biliary tree.
6. Bile excreted from liver to gut and de-conjugated.

Question 15

What pigment gives faeces brown colour?

Answer 15

• Stercobilin.

Question 16

What gives urine yellow colour?

Answer 16

• Urinobilin.

Question 17

What is jaundice?

Answer 17

• Hyperbilirubinemia.

Question 18

Discuss the classifications of jaundice.

Answer 18

1. Pre-hepatic: haemolytic.
2. Intra-hepatic: viral, drugs
3. Post-hepatic: obstruction

Question 19

What is pre-hepatic jaundice?

Answer 19

• Haemolytic jaundice.
• Bilirubin production is exceeding liver uptake capacity.
• Commonly due to autoimmune dx: Rh- incompatibility, sickle cell dx, haemolytic disease of newborn.
• Unconjugated

Question 20

What is intrahepatic jaundice?

Answer 20

• Hepatocellular jaundice.
• Problem within hepatocytes function.
• Impaired uptake, conjugation or secretion.
• Unconjugated or conjugated.

Question 21

What is post-hepatic jaundice?

Answer 21

• Obstructive/ choleostatic jaundice.
• Obstruction in biliary tract.
• Conjugated bilirubin regurgitated back into systemic circulation.
• Pale stools + dark urine.

Question 22

What is Kernicterus (bilirubin encephalopathy)?

Answer 22

• Results from untreated hyperbilirubinemia w/bilirubin levels 25 or higher.
• Signs: lethargy, tonic motions such as backward arching of the neck and trunk, hypotonia.

Question 23

What is Gilbert’s syndrome?

Answer 23

• Benign congenital unconjugated hyperbilirubinemia.
• Defect in UDP glucuronyl transferase.
• Treatment: phenobarbitone.

Question 24

What is Crigler-Najjar syndrome?

Answer 24

• Congenital unconjugated hyperbilirubinemia.
• Defect in UDP glucuronyl transferase.
• Type 1&2.

Question 25

What is Dubin- Johnson syndrome and Rotor Syndrome?

Answer 25

• Benign autosomal recessive disorders presenting with conjugated hyperbilirubinemia.
• Characterised by impaired biliary secretion of conjugated bilirubin.
• Grossly black liver. Benign.
• Mutation in MRP2 (DJS).