Liver Function Tests Flashcards
Enzymes analysed (3)
Serum Transaminases (ALT/AST) Alkaline Phosphatase (ALP) Gamma Glutamyl Transpeptidase (GGT)
Indices of intrinsic synthetic function (3)
Albumin
Prothrombin Time/INR
Bilirubin - Context for disease
Transaminases (2)
Intracellular but released from hepatocytes upon injury
Catalyses gamma-amino group transfers
Alanine aminotransferase (ALT) (4)
Most common
More sensitive than AST
Predominantly cytosol-located and Liver
Short half-life of 47 hours
Aspartate aminotransferase (AST) (3)
In cytosol and mitochondria
Present in Liver, Heart, Pancreas, Skeletal muscle, Brain, Lungs, RBCs, WBCs
Half Life of 17 hours
Aminotransferases (7)
Often become deranged in all aetiologies
Marked increase in hepatocellular pathologies
Levels may/may not reflect extent of damage
Do not correlate with outcomes
Usually less than 500 U/L in obstructive jaundice
Except acute phase of biliary obstruction with passage of stone into CBD. This process may coincide with ALT values >1-2,000 U/L
This is often a very transient phenomenon and indices revert back to that of more cholestatic picture
Alkaline Phosphatase (3)
Catalyses hydrolysis of organic phosphate esters
Half life of 1 week
Originates in biliary, bone placenta, intestine, kidney
Gamma Glutamyl Transpeptidase (GGT) (6)
Involved in gluthionine metabolism, transfer of amino acids across cellular membranes and leukotriene metabolism
Present in cell membrane of liver, kidneys, bile duct, pancreas, gallbladder, spleen, heart, brain, and seminal vesicle - Not bone
Used as a diagnostic marker for liver or cholestatic diseases
Useful in determining whether elevated ALP is of bone or liver origin
GGT is “inducible”- Drugs particularly anticonvulsants and TCAs and Paracetamol. Diabetes mellitus, pancreatic disease, COPD, renal disease
Levels can be increased alcohol consumption
Bilirubin
Breakdown product of haem
Uptake into the hepatocytes
Undergoes conjugation
Excreted via urine/faeces
Isolated Hyperbilirubinaemia (2)
When LFTs are normal except elevated bilirubin
Classed in conjugated or unconjugated
Prothrombin time (2)
Measure conversion time from Prothrombin to Thrombin
Increased levels indicate reduced synthetic functionality, drugs (Warfarin), Bile malabsorption (Vitamin K deficiency), consumptive coagulopathies, congenital coagulopathy
History taking main points (7)
Use of any chemical or medication
Accompanying symptoms - Pruritus, jaundice, arthralgia, weight loss, exanthema, fever, anorexia
Parenteral exposures - IV medications/blood transfusions, intranasal drugs, tattoos and sexual history
Travel history including timings and exposure risks (contact with exotic zoonosis)
Alcohol exposure - Duration, units consumed
Occupational exposures
Temporal variation
Medications (2)
LOOK AT TIMINGS - What has changed
Watch for Antibiotics, antidepressants, statins, Sulfonamides, NSAIDs, anti-epileptics, anti-TB medications, OTC medication
ALT > ALP and increased or normal bilirubin indicates
Hepatocellular injury
ALP > ALT with increased bilirubin indicates
Cholestasis
Increased INR indicates (3)
Prolonged Jaundice
Vitamin K Malabsorption
Hepatocellular Dysfunction
Acute hepatocellular injury picture (5)
Use AST:ALT ratio - Normal is 0.8, >2 suggests alcohol
Need liver screen from hepatitis, HIV, EBV, HSV (For pregnant or immunocomprimised)
Carry out doppler ultrasound
Review medication
Presence of hypotension episodes
Mimic or overlapping conditions to acute hepatocellular injury (6)
Coeliac Disease Muscle disorders (Myositis, Rhabdomyolysis) Creatine Kinase (CK) Adrenal Insufficiency Anorexia Nervosa Thyroid Disorders
Rare causes for Acute hepatocellular injury (4)
Autoimmune hepatitis
Wilsons disease
Haemochromatosis
α1 Anti-trypsin deficiency
Unconjugated Hyperbilirubinaemia causes (3)
Increased bilirubin production - Haemolysis, extravasation of blood into tissues
Impaired hepatic bilirubin uptake - Heart failure, portosystemic shunts, Drugs
Impaired bilirubin conjugation -
Hyperthyroidism, Advanced Liver Disease
Conjugated Hyperbilirubinaemia causes (3)
Extrahepatic Cholestasis (Biliary Obstruction) - Acute/Chronic pancreatitis, cholelithiasis, cholangiocarcinoma, head of pancreatic tumour
Intrahepatic Cholectasis - Sepsis, cirrhosis, infiltrative diseases, acute hepatitis
Drugs - Alkylated steroids, Rifampicin
Acute liver failure presentations (3)
Jaundice
Encephalopathy - Brain disease/damage
Coagulopathy - Bleeding disorder
Maximum dose of paracetamol daily
4g
What does smooth muscle antibody test indicate
Autoimmune disease
