6b.) Jaundice & LFTs Flashcards
What is jaundice?
Yellowing of skin and sclera due to raised plasma bilirubin (hyperbilirubinaemia)
Where does bilirubin come from?
Breakdown product of haem
Bilirubin can be unconjugated and conjugated…
- What is it bound to when unconjugated?
- Where is it conjugated?
- What does conjugation do to properties of bilirubin?
- Unconjugated bound to albumin
- Conjugated in liver
- Conjugation makes it water soluble
Describe bilirubin metabolims
State the 3 main causes/types of jaundice and state what causes each
- Pre-hepatic: too much haem due to haemolysis
- Hepatic: reduced hepatic function so liver can’t metabolise haem efficiently
- Post-hepatic: obstructive causes
Describe pre-hepatic jaundice, include:
- Why it occurs
- In what form is the raised bilirubin, conjugated or unconjugated?
- Some common causes
- Increased haemolysis leading to increased degradation of haemoglobin leading to too much haem; liver cannot cope
- Unconjugated bilirubin levels raised
- Common causes are haemoglobinopathies e.g.:
- Sickle cell
- Thalassaemia
- Spherocytosis
- OR damage to RBCs
State a complication of jaundice in neonates
Kernicterus: permanent brain damage
Describe hepatic jaundice, include:
- Why it occurs
- In what form is the raised bilirubin, conjugated or unconjugated?
- Some common causes
- Occurs because there is hepatocellular damage which means the conjugating ability of the liver is reduced. *NOTE: excretion pathway is usually fine but can sometimes get a mixture of hepatic & post hepatic
- Mix of conjugated and unconjuaged bilirubin
- Causes of hepatic jaundice:
- Chronic liver damage e.g. cirrhosis (see image for causes of cirrhosis)
- Actue liver damage e.g. paracetamol toxicity, viral hepatitis (acute) and other infections
Describe post-hepatic jaundice, include:
- Why it occurs
- In what form is the raised bilirubin, conjugated or unconjugated?
- Some common causes
- Obstruction in excretion pathway/biliary tree NOTE: conjugating ability of liver usualy fine but sometimes can get mixture of hepatic and post -hepatic
- Raised bilirubin= conjugated
- Causes:
- Gallstones
- Biliary stricture (common in paeds)
- Pathology of head of pancreas
- Intrahepatic pathology that is compressin intrahepatic bile ducts e.g. oedema due to inflammation, growth such as malignancy, scarring such as cirhosis
If someone presents with dark urine and pale stools; which “type” of jaundice do you suspect and why?
- Post-hepatic
- Dark urine: raised bilirubin is conjugated, conjugated bilirubin is more soluble, more excreted by kidneys
- Pale stools: bile excretion into bowel is blocked; it is bilirubin that usually gives faeces colour
Is bilirubin pigmented?
Yes
What can we measure in liver function tests? (5)
Which tell us about function and which are markers of liver damage?
- Bilirubin (conjugated & unconjugated- often just given total if don’t specify)
- Albumin
- Alanine transaminase (ALT)
- Aspartate aminotransferase (AST)
- Alkaline phosphatase (ALP)
First 2 tell us about liver function. Last 3 are markers of liver damage
Explain why albumin can be used as in indicator of liver function
Albumin made by liver hence if liver function reduced then less albumin will be made. NOTE: liver makes other proteins too which can also be measured, also makes clotting factors
What are ascites?
Explain how low albumin can contribute to ascites
State another causes of ascites
- Ascites= presence of excess fluid in the peritoneal cavity
- Albumin contributes to oncotic pressure of plasma so low albumin means low oncotic pressure which means fluid is more likley to leak out of vascularture and into peritoneal cavity
- Can also occur due to liver cirrhosis. Cirrhosis can cause portal hypertension which can lead to swelling of portal vein which can then block lymph channels and cause the lymph to spill into abdomen
State two causes of hypoalbuminaemia
- Liver disease e.g. cirrhosis
- Kidney damage (albumin excreted when it shouldn’t be)
When are ALT and AST released?
When liver damage has occured
Which out of alanine transaminase (ALT) and aspartate transaminase (AST) is more specific to the liver and why?
ALT is more specific to liver because AST is also found in cardiac/skeletal muscle and RBCs
Which rises more ALT or AST in acute liver damage?
ALT > AST
Which rises more ALT or AST in cirrhosis and alcoholic hepatitis?
AST > ALT
Where is alkaline phosphatase (ALP) found?
State 2 causes for raised ALT
How can we differentiate between the 2 causes
- Cells lining biliary tree
- Raised ALT due to:
- Cholestasis (bile duct obstruction)
- From bones during growth (child)
- Use Gamma-Glutamyl Transferase (Gamma GT) to specify source as liver
If you have a high ALT and high gamma GT what does this suggest?
High ALT is due to problem with liver
What does an LFT with:
- Raised ALT and AST
.. indicate?
Hepatocellular damage
What does an LFT with:
- Raised ALP
… indicate?
Obstructive problem
What does an LFT with:
- Raised bilirubin
- Raised ALT and AST
- Raised ALP
Hepatocellular damage and obstructive
**REMEMBER: can only say it’s jaundice if you see the jaundice. High bilirubin does not equal jaundice all the time
Summarise for each of the 3 “types” of jaundice:
- If high bilirubin will be conjugated or unconjugated
- ALT and AST
- ALP
Read following case and state the likely cause and type of jaundice
Hepatocellular damage- hepatic jaundice
Read the following case and state the likely cause and suggest a possible diagnosis
Obstructive cause.
Sounds like pancreatitis- could confirm with amylase
Answer the following
C
Answer the following
E
Explain why malignancy in head of pancreas can cause jaundice
Block part of biliary tree leading to post-hepatic jaundice
