chempath tutorial 3 - jaundice & liver function tests Flashcards
What are the visible manifestations of jaundice?
Yellowing of the skin, mucus membranes and the sclera of the eyes
Why may transient jaundice occcur in a premature infant?
Their bilirubin conjugating systems are immature, and there will be increased breakdown of fetal red blood cells releasing bilirubin
What happens to plasma levels of total bilirubin in haemolytic anaemia?
Increases
What happens to plasma levels of unconjugated in haemolytic anaemia?
Increases
What happens to plasma levels of conjugated bilirubin in haemolytic anaemia?
Stays normal
What happens to levels of urine urobilinogen in haemolytic anaemia?
Increases
What happens to levels of urine bilirubin in haemolytic anaemia, and why?
Not present (because urine bilirubin is conjugated, but levels of conjugated do not rise in haemolytic anaemia because hepatobiliary function is normal
What happens to plasma levels of total bilirubin in cholestasis?
Increase markedly
What happens to plasma levels of unconjugated in cholestasis?
modest increase or stays normal
What happens to plasma levels of conjugated bilirubin in cholestasis?
Marked increase
What happens to levels of urine urobilinogen in cholestasis?
Decreases
What happens to urine bilirubin levels in cholestasis?
They increase/is present
Why do urobilinogen levels in the liver decrease with cholestasis?
There is less conjugated bilirubin being excreted into the intestines and converted to urobilinogen, and therefore a decreased level in theurine
What is the difference between bile pigments and bile salts?
Bile pigments are the coloured derivatives of the breakdown of Haem, while bile salts are derived from cholesterol and are used in lipid digestion and absorption
How do plasma cholesterol levels change with cholestasis?
Tend to rise
How do plasma cholesterol levels change with chronic hepatocyte damage?
Fall
In what sorts of liver disease is the determination of the activities of aspartate and alanine aminotransferases (AST and ALT) in plasma useful as a diagnostic acid?
when there has been liver cell damage or necrosis, especially acute
In what sorts of liver disease is the determination of the activities of alkaline phosphatase and gamma glutamyltransferase in plasma useful as a diagnostic acid?
Cholestasis (intrahepatic or extrahepatic), alcoholic liver disease
What type of jaundice does cirrhosis cause?
Intrahepatic obstructive jaundice
How can a liver function test differentiate cirrhosis from acute hepatitis?
In acute hepatitis, there is no change in the ability of the liver to produce proteins, so albumin levels will be normal, while they will be markedly low in a poorly functioning cirrhotic liver.
In a case of extrahepatic biliary obstruction, what would you expect the levels of plasma alanine aminotransferase to be?
Mildy/moderately elevated
In a case of extrahepatic biliary obstruction, what would you expect the levels of plasma cholesterol to be?
elevated due to failure to excrete
In a case of extrahepatic biliary obstruction, what would you expect the levels of prothrombin to be?
low
In a case of extrahepatic biliary obstruction, what would you expect the levels of gamma glutamyl transferase to be?
High
In a case of extrahepatic biliary obstruction, what would you expect the levels of urine bilirubin to be?
high
In a case of liver cirrhosis, what would you expect the levels of plasma alanine aminotransferase to be?
Mildy/moderately elevated (may be normal)
In a case of liver cirrhosis, what would you expect the levels of cholesterol to be?
Low due to cell damage reducing synthesis
In a case of liver cirrhosis, what would you expect the levels of prothrombin to be?
Low
In a case of liver cirrhosis, what would you expect the levels of gamma glutamyl transferase to be?
High, if alcoholic liver disease present
In a case of liver cirrhosis, what would you expect the levels of urine bilirubin to be?
elevated
What is bilirubin bound to in the blood?
Albumin
What are the 3 key ways that drugs may lead to jaundice?
- Promote haemolysis
- Inhibit bilirubin conjugation
- Damage liver cells/cause hepatitis reactions/cause cholestasis
Why is prothrombin concentration reduced in patients with cholestasis?
Because of a lack of absorption of Vitamin K, which is a fat soluble vitamin, because of limited secretion of bile salts into the intestine that are required for lipid digestion/uptake.
Why can increased prothrombin time in a patient with jaundice be reversed with Vitamin K in cases of cholestasis, but not cirrhosis?
With cholestasis, issue is low vitamin K to activate clotting factors, which can be reversed with infusion.
In cirrhosis, there is liver damage reducing the number of factors being produced, meaning vitamin K will not help.
