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Pathogenesis of hepatic encephalopathy

Hepatic encephalopathy is a complex neuro psychiatric syndrome that is caused by liver disease. 
This will manifests as disturbances in
1.Consciousness and behaviour.
2.Personality changes.
4.Distinctive electroencephalographic changes
It may present as 
Acute and reversible form
Chronic and progressive form
Severe cases  may leads to coma, later on death 
Occur in severe hepatocellular dysfunction.

Main  mechanism of hepatic encephalopathy is porto systemic shunting of blood.
This is a complication of portal HTN.
There is obstruction to the passage of blood  absorbed from the intestine to go through liver. As there is no valves in the portal venous system it will facilitates retrograde blood flow to the lower pressure systemic venous circulation. So the portal blood bypass the liver and it reaches the systemic circulation without undergoing the 1st pass detoxification. There is portal systemic collateral formation.The major sites of collateral are Gastro oesophageal junction, umbilicus, anal canal and posterior abdominal wall.

Toxic substances accumulated in hepatic encephalopathy are
False neurotransmitters
Mercaptans(methionine metabolism)
Short chain fatty acids
GABA(Gama-aminobutyricacid) inhibitory neurotransmitter
Endogenous benzodiazepine acting through GABA receptors 
What these neurotransmitters will do?
1. These neurotransmitters will causes the supporting cells of the brain (astrocytes) to swell. Which inturn increases the intracranial pressure, leading  to herniation of brainstem and death
2. There will be disruption of the blood brain barrier leading to cerebral edema.