Physiology Portal HTN

Question 1

Go over slides for recap

Answer 1

xx

Question 2

List consequences of portal HTN.

Answer 2

Oesophageal varices
Hepatic encephalopathy
Ascites
Impaired liver function

Question 3

What are varices?

Answer 3

Dilation of pre-existing blood vessels.

Question 4

What does portal hypertension lead to?

Answer 4

Shunting of blood from the portal vein to the systemic (venous) circulation

Question 5

What may happen to varices?

Answer 5

Thin-walled varices may rupture with increased venous pressure (15-20mmHg)
Also can be torn by bulky food passing through the oesophagus

Question 6

What does bleeding from varices cause?

Answer 6

Follows on from rupture.
Steady regular bleeding may cause anaemia
In severe cases, acute haemorrhage may occur
Haematemesis = vomit up blood

Question 7

How do we treat haemodynamic changes found in portal HTN?

Answer 7

Destruction of varices - sclerotherapy or banding
Drug therapy - vasoconstrictors diminish portal vein inflow from the GI tract
Surgery - shunt surgery, TIPS (transjugular intrahepatic portosystemic shunting), transplantation

Question 8

What causes hepatic encephalopathy?

Answer 8

Reduced hepatic detoxification
Toxins (NH3) bypass liver via shunts (protein)
Cerebral dysfunction/neuropsychiatric symptoms

Question 9

What is ascites and what causes it?

Answer 9

Accumulation of peritoneal fluid
Increased hydrostatic pressure
Low COP - albumin

Question 10

Define hepatic encephalopathy.

Answer 10

Cerebral dysfunction associated with liver failure.
Gradual/chronic - acute/fulminant
Neuropsychiatric symptoms/signs

Question 11

What are the signs of hepatic encephalopathy?

Answer 11

Chronic - personality changes, sleep changes, incoordination, asterixis (hand flap)
Acute - rapid progression from altered mental state –> coma, seizures, cerebral oedema

Question 12

What is the pathogenesis behind hepatic encephalopathy?

Answer 12

Hepatic detoxification - reduced capacity/bypasses the liver
Blood-brain barrier changes in permeability

Question 13

What toxins are involved in hepatic encephalopathy and how?

Answer 13

Ammonia
Gut bacteria vs proteins/urea = normal detoxification
Normally liver detoxifies.
In liver failure we can’t detoxify or it doesn’t get to the liver due to shunt = increased levels in systemic circulation

Question 14

What is the function of astrocytes in hepatic encephalopathy?

Answer 14

Usually detoxify ammonia, but increased levels of ammonia overwhelm the astrocytes
This leads to glutamine accumulation/Na-K-ATPase
Resulting in swelling/BBB impaired

Question 15

What other toxins can cause hepatic encephalopathy?

Answer 15

Mercaptans (sulfur containing compounds)
GABA-like compounds
Short chain FAs, aromatic AAs
Manganese

Question 16

List precipitating factors for hepatic encephalopathy.

Answer 16

GI bleed (more protein in GI tract) 
High protein intake
Constipation 
Metabolic
Infection
Alcohol/neurodepressants
Shunts (TIPS)

Question 17

How do you diagnose hepatic encephalopathy?

Answer 17

Overall picture/history of liver disease
Exclude other causes
Impaired neuropsychological performance
Asterixis (flapping tremor)
Elevated serum ammonia concentrations
CSF - increased protein
EEF (electro-encephalic gram) - reduced frequency

Question 18

What is the management for hepatic encephalopathy?

Answer 18

Care 
Precipitating factor treatment 
Lactulose - laxative for constipation 
Antibiotics
Diet - decrease proteins 
P-V shunt (TIPS) 
Transplant

Question 19

What is ascites and what disorders cause it?

Answer 19

Excess of peritoneal fluid - common complication of cirrhosis/portal HTN

Question 20

Describe why ascites is serious.

Answer 20

Median survival 2 years from onset of ascites
Survival depends mainly on liver function
Spontaneous Bacterial Peritonitis in 25% of cases
Low urinary sodium and SBP predict high mortality

Question 21

What is the pathophysiology behind ascites?

Answer 21

Increased hydrostatic pressure - lymph loss
Reduced COP
Sodium and fluid retention

Question 22

What is the management for ascites?

Answer 22

Limit sodium intake
Bed rest
Diuretics - spironolactone 
Paracentesis - drains ascites 
P-V shunt (TIPS) 
Transplant