LFTs Flashcards
what are the hepatic enzymes in LFTs?
serum transaminases (ALT/AST)
Alkaline phosphatase
Gamma Glutamyl Transpeptidase
what are the indicators of intrinsic synthetic function?
albumin
Prothrombin time
Bilirubin
hepatic enzymes are usually intracellular, when are they released from hepatocytes?
hepatocellular injury
what do hepatic enzymes do?
catalyse gamma-amino acids
how does damage affect aminotransferase?
often raised in all aetiologies/hepatocellular pathologies
usually less than 500 in obstructive jaundice
what does ALP do?
enzyme that catalyses the hydrolyses of a number of organic phosphate esters
what is the pathway of bilirubin?
breakdown of haem transported to liver bound to albumin uptake into hepatocytes undergoes conjugation excreted via urine/faeces
what is isolated hyperbilirubinaemia?
high bilirubin either conjugated or unconjugated
what clotting factors does the liver synthesise?
factor 1 (fibrinogen) factor 2 (prothrombin) 5 7 9 10 13
what does prothrombin time measure?
conversion time from PT to thrombin
what does elevated PT indicate?
reduced synthetic functionality
what can cause elevated PT?
Drugs (warfarin)
bile malabsorption - Vit K deficiency (common in gall stones, cholangitis)
consumptive coagulopathy
important history Questions?
use/exposure to chemicals/drugs
accompanying symptoms
parenteral exposures (tattoos, sex, blood transfusions, snorting drugs)
travel history
alcohol exposure
occupational exposure
temporal variation (eg. cholestatic = itchy at night)
name some drugs that can cause deranged liver tests
antibiotics antidepressants statins NSAIDs Anti-epileptics Anti-TB (anti-TNF alpha) sulphonamides/sulphonylureas Over the counter
ALT/AST > Bili N/?
hepatocellular
ALP > ALT/AST
Increased Bili?
cholestasis
increased PT/INR?
prolonged jaundice/vit K malabsorption
hepatocellular dysfunction
Albumin means?
difficult to isolate
what is the picture of acute hepatocellular injury?
AST:ALT ration more than 0.8 need acute liver screen for hepatitis, HIV and other viruses (consider HSV if pregnant) Doppler ultrasound review medications possible hypertension
what mimic/overlap conditions can cause raised AST:ALT?
coeliac disease muscle disorders adrenal sufficiency anorexia thyroid
how can you exclude coeliac disease?
tTG - IgA
consider HLA testing
gold standard = biopsy
what is caused by unconjugated hyperbilirubinaemia?
increased bilirubin production
impaired hepatic bilirubin uptake
impaired bilirubin conjugation
what can cause impaired bilirubin uptake in hepatocytes?
heart failure
portosystemic shunts
drugs - rifampicin, probenacid
what canc cause impaired bilirubin conjugation?
gilberts/CN type 2
hyperthyroidism
liver disease
what occurs with conjugated hyperbilirubinaemia?
Extrahepatic cholestasis (biliary obstruction) Intrahepatic cholestasis (cirrhosis, sepsis,TPN, hepatitis)
what are the signs of acute liver failure?
jaundice
encephalopathy
..
what is a cholestatic picture in LFTs?
raised alkaline phosphatase raised bilirubin (not always a huge amount)
what can CMV and EBV virus cause?
splenomegaly
