Jaundice + LFTs Flashcards
what blood tests are taken to measure liver function
Bilirubin Albumin Prothrombin Time (PT) ALP (alkaline phosphatase) AST + ALT GGT
which LFTs measure the livers synthetic function
Bilirubin, Albumin, PT
which LFTs demonstrate hepatocellular damage
AST + ALT
which LFT is significantly raised in cholestasis
ALP
what is bilirubin
a normal breakdown product of Haem metabolism
where is bilirubin conjugated
the liver
- then excreted via bile into GI tract
what happens to bilirubin that is excreted into GI tract
majority egested in faeces as urobilinogen + stercobilin (colours faeces)
roughly 10% is reaborbed into bloodstream + excreted by kidneys
what is jaundice
the yellow discolouration of the sclera / skin as a result of hyperbilirubinaemia
what are the three types of jaundice
pre-hepatic
hepatic
post-hepatic
what is the mechanism of pre-hepatic jaundice
excessive red blood cell breakdown
LFT results pre-hepatic jaundice
isolated rise in bilirubin
- bilirubin is unconjugated as has not undergone conjugation in liver
- normal AST, ALT, ALP
causes of pre-hepatic jaundice
Gilberts syndrome
Haemolytic anaemia
what is Gilberts syndrome
autosomal recessive condition causing defective bilirubin conjugation
- deficiency of UDP glucuronosyltransferase
- jaundice during illness, fasting, exercise
LFTs in Gilberts syndrome
isolated rise unconjugated bilirubin
what is the mechanism of hepatic jaundice
dysfunction of hepatic cells
causes of hepatic jaundice
alcoholic liver disease viral hepatitis autoimmune hepatitis medications haemochromatosis hepatocellular carcinoma primary sclerosis cholangitis primary biliary cirrhosis
LFT results in hepatic jaundice
raised bilirubin (unconjugated + conjugated) a greater raised ALT/AST than ALP
what is the mechanism of post-hepatic jaundice
obstruction of biliary drainage – cholestasis
causes of post-hepatic jaundice
intraluminal - gallstones
mural - cholangiocarcinoma, strictures
extra-mural- pancreatic cancer, lymphoma
LFT results in post-hepatic jaundice
raised bilirubin (conjugated) a greater rise in ALP than ALT/AST
normal colour of urine + stools suggests which type of jaundice
pre-hepatic
dark urine + normal colour stools suggests which type of jaundice
hepatic
dark urine + pale stools suggests which type of jaundice
post-hepatic
what can cause an isolated GGT rise
alcohol
phenytoin
(raised GGT + markedly raised ALP = cholestasis)
what can cause an isolated rise in ALP
anything that leads to increased bone breakdown:
- bony mets / primary bone tumour
- vit D deficiency
- recent bone fractures
- renal osteodystrophy
what are the main synthetic functions of the liver
conjugation + elimination of bilirubin
synthesis of albumin
synthesis of clotting factors
Gluconeogenesis
how can the synthetic function of the liver be assessed
by measuring:
- serum bilirubin
- serum albumin
- PT time
- blood glucose
what is the function of albumin
helps to bind water, cations, fatty acids and bilirubin
what can cause low albumin
liver disease, e.g. cirrhosis, causing low levels to be produced
nephrotic syndrome
acute inflammation that causes suppression of livers production
what can cause a high albumin
dehydration
how does liver dysfunction affect PT time
causes increased PT time due to impaired synthesis of clotting factors
common causes of acute hepatocellular injury
poisoning – paracetamol overdose
infection – hepatitis A + B
liver ischaemia
what is cholestatic pruritis
generalised itch that occurs with post hepatic jaundice
- accumulation of bile salts below skin causes inflammatory response
- often worse at night + exacerbated by heat
- no sin lesions
tx of cholestatic pruritis
mild - topical menthol cream
mod/severe - cholestyramine
