Jaundice and LFT's Flashcards
What is jaundice?
clinical manifestation of raised bilirubin
-seen in the sclera of the eyes and in the skin
What is the metabolism of bilirubin?
splenic macrophages engulf and digest erythrocytes (RBC) and the Hb is broken down into Haem and globi
- the haem forms bilirubin that is unconjugated
- this is deposited in the liver where it is conjugated (meaning it is now water soluble)
- 3 pathways;
- can either travel as bile in the enterohepatic circulation
- go to the kidney and be excreted in urine
- go to the gut and be excreted as faeces
What does unconjugaed mean?
not water soluble so has to travel round attached to albumin
What are the 3 causes of jaundice?
- pre-hepatic (too much haem)
- hepatic (reduced hepatocyte function)
- post-hepatic (obstructive causes)
How is pre-hepatic jaundice caused?
- increased degradation of haemoglobin
- the liver conjugating ability and excretion pathway is fine
- but too much demand on liver so levels of bilirubin that are raised tend to be unconjugated
What are common causes of pre-hepatic jaundice?
- haemoglobinopathies e.g. sick cell, thalassaemia, spherocytosis
- damage to RBC (haemolysis)
How is hepatic jaundice caused?
- caused by reduced conjugating ability of the liver due to damage to hepatocytes
- amount of bilirubin and excretion pathway are usually fine
- will get a mix of conjugated and unconjugated bilirubin
What are common causes of hepatic jaundice?
- cirrhosis
- paracetemol toxicity
- viral hepatitis
- other infections
- alcoholic liver disease
- NAFLD
- wilsons disease
- hereditary haemochroatosis
- mediciation
- autoimmune
What is post-hepatic jaundice?
caused by obstruction to the excretion pathway
- amount of bilirubin and conjugating ability is usually fine
- raised bilirubin tends to be conjugated
What can a patient present with with post-hepatic jaundice?
As the conjugated bilirubin is water soluble, more is going to be excreted by the kidneys and as bilirubin is pigmented
-makes dark urine and pale stools (due to it not entering the GI system)
What are some common causes of post-hepatic jaundice?
- gallstones
- biliary stricture
- anythig blocking common bile duct
- pathology of the head of the pancreas
- intra-hepatic pathology can compress the intrahepatic bile ducts causing oedema, malignancy and scarring (cirrhosis)
What are the different types of liver function tests?
- bilirubin (unconjugated vs conjugated)
- albumin
- ALT (alanine transaminase)
- AST (aspartate aminotransferase)
- ALP (alkaline phosphatase)
What is albumin?
-major serum protein
Why is albumin levels assessed?
assess the synthetic function of the liver e.g. if liver function is reduced, less albumin is synthesised
What does low albumin contribute to?
ascites
Why are ALT and AST measured?
-these are hepatic enzymes so if hepatocytes are damaged, these enzyme levels go up
Which enzyme is most specific to the liver?
ALT
-AST also found in cardia/skeletal muscle and RBC
What would the enzymes show in acute liver damage?
ALT rises more than AST
What would the enzymes show in cirrhosis or alcoholic hepatitis?
AST rises more than ALT
What is ALP?
Alkaline phosphatase which is found in the cells lining the bile ducts
When would levels of ALP rise?
in cholestatsis (bile duct obstruction)
What are other causes of raised ALP?
-high bone turnover
How can you make sure that raised ALP is due to liver?
Gamma GT (also goes up in liver/bile ducts)
What do LFT’s show you?
tell you the underlying liver pathology
- hepatocellular damage
- obstructive (cholestasis)
- mixed (damage to hepatocytes and obstruction)
