Liver Failure Flashcards
What is jaundice characterised by?
Elevated unconjugated serum BR levels →Yellowish pigmentation
What is the normal plasma [BR]?
17 micromol/L
If [BR] is elevated > 30 micromol/L what happens?
Yellow sclera and mucous membranes
If [BR] is elevated > 34 micromol/L what happens?
Skin turns yellow
Define cholestasis.
Slow/cessation of bile flow due to impaired secretion by hepatocytes or a result of obstructive flow through common hepatic/bile ducts or MPDs.
What does cholestasis normally result in and how?
Jaundice
^ bile and BR retention within hepatocytes (Conjugated BR and bile are unable to enter the duodenum)
If a patient has jaundice does it mean they will have cholestasis?
No
List the pre-hepatic causes of jaundice.
Haemolysis - haemolytic anaemia + toxins
Ineffective erythropoiesis
Massive transfusion (transfused erythrocytes short lived) - Large haematoma resorption
What diseases can lead to haemolysis (haemolytic anaemia)?
SCA and healthy spherocytes undergo haemolysis within the spleen, whereby the haem oxidative cleavage proceeds producing unconjugated BR → Serum concentration increases.
What is a haematoma and how can it cause jaundice?
Collection of erythrocytes deep to skin. Degradation and haemolysis of erythrocytes within a large haematoma will resultantly produce aberrant levels of unconjugated BR levels for resorption.
List the intrahepatic causes of jaundice.
Gilbert Syndrome = decreased uptake of BR Crigler-Najjar Syndrome = decreased conjugation of BR Dubin-Johnson and Rotor Syndrome = reduced BR secretion into biliary canaliculi → Black liver Intrahepatic cholestasis (decreased outflow) = Sepsis, TPN and drugs LF (acute/chronic)
What does Dubin-Johnson and Rotor Syndrome do to conjugated BR levels in plasma?
Increase
What is Gilbert syndrome?
Autosomal recessive due to a mutation in UGT1A1 gene → decreased activity of bilirubin diphosphate glucuronosyltransferase enzyme. Reduced uptake of BR into hepatocytes subsequently increase serum unconjugated BR levels within sinusoidal space and systemic circulation.
Explain the pathogenesis of LF.
Rate of hepatocyte death > regeneration.
Combination of apoptosis and/or necrosis - necroptosis.
Hepatocyte death is attributed with a combination of apoptosis (acetaminophen=paracetamol) and necrosis (ischaemia).
Within a hepatic acinus, Zone 3 (central vein region) is sensitive to necrosis and ischaemia due to its relative distance to oxygenated blood supply.
N.B. Clinically, LF is concerned with coma/death due to multi-organ failure.
What are the 2 types of acute LF?
Fulminant or sub-fulminant
Define fulminant hepatic failure (type of ALF).
Rapid development (<8 weeks) of severe acute liver injury. Impaired synthetic function (INR/PT, albumin) resulting in hypoalbuminemia.
Encephalopathy
What is encephalopathy?
Pathological impairment of the brain. Well-compensated liver disease.
Define sub-fulminant hepatic failure (type of ALF).
<6 months
Define chronic LF.
Failure persisting for a period greater than 6 months, concerned with liver cirrhosis.
What are the common causes of ALF in the west?
Paracetamol (deliberate overdose)
Amanita phalloides
Bacillus cereus
What are the common causes of ALF in the east?
Exacerbations of chronic Hep B (Hong Kong) Hep E (India)
How does paracetamol overdose lead to ALF?
N-acetyl-p-benzoquinone imine (NAPQI) metabolites is conjugated with glutathione, inhibiting cellular enzymes (Glutamine dehydrogenase) and impairing mitochondrial respiration (Inhibits cytochromes and uncouples OP). Superoxide anion formation directly kills hepatocytes via oxidative stress.
How does amanita phalloides lead to ALF?
Toxin inhibit RNA polymerase → Reduction of PS → Cell necrosis
How does bacillus sereus lead to ALF?
Inhibition of hepatocyte mitochondrial Beta-oxidation
List diseases of pregnancy that can cause ALF.
Acute fatty liver of pregnancy (AFLP)
HELLP (Haemolysis Elevated Liver enzyme Low Platelet count)
HEV
Budd-Chiari
Explain how AFLP + HELLP leads to ALF.
Haemolysis, elevated liver enzymes and a low platelet count (HELLP) syndrome → DIC. Hepatic infarction of hepatic portal veins and arteries.
Explain how Budd Chiari syndrome leads to ALF.
Vascular occlusion of central veins and hepatic veins (left, right and middle hepatic veins are thrombosed).
List the idiosyncratic drug reactions that cause ALF.
Single agent: Isoniazid, NSAIDs, valproate.
Drug combinations: Amoxicillin/clavulanic acid, trimethoprim/sulphamethoxazol, rifampin/isoniazid.
What vascular diseases can cause ALF?
Ischaemia hepatitis
Post-OLTx hepatic artery thrombosis
Post-arrest
Veno-occlusive disease (VOD).
What metabolic diseases can cause ALF?
Wilson’s disease → Elevated Cu2+ deposition.
Reye’s syndrome → Hepatic swelling post viral infection (aspiring prescription), prevalent in infants.