case 5 - jaundice and cirrhosis Flashcards
what does jaundice refer to
the yellowish tint to the body tissues
what is it caused by
large amounts of billirubin in the extracellular fluids
what are the three types of jaundice
pre-hepatic
intra-hepatic
post-hepatic
what is the normal plasma concentration
The normal plasma concentration of bilirubin, which is almost entirely the free form, averages 0.5 mg/dl of plasma.
when will the skin begin to appear jaundiced
when the concentration rises to about three times normal - above 1.5mg/dl
what is pre hepatic jaundice caused by
haemolysis or by congenital hyperbillirubinaemia and is characterised by an isolated raised bilirubin level
what is haemolysis
this is the destruction of RBCs or their precursors in the bone marrow.
this causes increased bilirubin production
therefore the plasma concentration of unconjugated bilirubin rises to above normal levels
why is jaundice due to haemolysis usually mild
because a healthy liver can excrete a bilirubin load six times greater than normal before unconjugated bilirubin accumulates in the plasma
what is intra hepatic jaundice caused by
impaired cellular uptake, defective conjugation or abnormal secretion of bilirubin by hepatocytes, occurring as a consequence of parenchymal liver disease
when can bilirubin transport across the hepatocytes be impaired
at any point between uptake of unconjugated bilirubin into the cells and transport of conjugated bilirubin into the canaliculi
what happens to the levels of both unconjugated and conjugated bilirubin in the blood
they both increase
what can hepatocellular jaundice be due to
acute or chronic liver injury and clinical features of acute or chronic liver disease may be detected clinically
what is jaundice due to parenchymal liver disease associated with
increases in AST, ALT, but increases in other LFTs, including GGT and ALP may occur and suggest specific aetiologies
what does acute jaundice in the present of raised AST suggest
an infectious cause
what is obstructive jaundice due to
Failure of hepatocytes to initiate bile flow.
Obstruction of bile flow in the bile ducts or portal tracts.
Obstruction of bile flow in the extrahepatic bile ducts between the porta hepatis and the papilla of Vater.
what happens to the unconjugated bilirubin
still enters the liver cells and becomes conjugated in the usual way
what happens to this conjugated bile
it is unable to enter the bile canaliculi and passes back into the blood
what is the consequence of this
most of the bilirubin in the plasma becomes the conjugated type rather than the unconjugated type
so why does this cholestatic jaundice occur
because the conjugated bilirubin is unable to enter the bile canaliculi and passes back into the blood
there is a failure of clearance of unconjugated bilirubin arriving at the liver
what happens when there is a total obstruction of bile flow
no bilirubin can reach the intestines to be converted into urobilinogen by bacteria
what happens when this urobilinogen isnt present
no urobilinogen is reabsorbed into the blood, and none can be excreted by the kidneys into the urine (urobilin)