Portal Hypertension

Question 1

Causes of portal hypertension (3)

Answer 1

1. Pre-hepatic
   - obstructive thrombosis of portal vein
   - splenomegaly w consequent increased splenic vein blood flow
2. Intra-hepatic
   - cirrhosis
   - schistosomiasis, massive fatty change, Caroli disease, sarcoidosis
3. Post-hepatic
   - severe R sided heart failure
   - constrictive pericarditis
   - hepatic vein outflow obstruction

Question 2

Pathogenesis of portal hypertension in cirrhosis (3)

Answer 2

1. Increased resistance to portal blood flow at level of hepatic sinusoids
   - parenchymal nodules compress sinusoids
   - contraction of vascular SM cells & myofibroblasts
2. Shunt formation
   - anastomoses b/w branches of hepatic artery & portal vein within fibrous septa - imposes high arterial pressure on the low pressure portal venous system
3. Increased portal blood flow (hyperdynamic circulation)
   - cirrhosis - impaired solute exchange b/w hepatocytes & plasma - reduced clearance of bacterial DNA absorbed from gut & carried to liver
   - stimulates NO prod - splanchnic arterial vasodilation

Question 3

Effects & complications of portal hypertension (4)

Answer 3

1. Ascites
2. Formation of portosystemic shunts
3. Congestive splenomegaly - anemia, thrombocytopenia, leukocytopenia
4. Hepatic encephalopathy - due to hyperammonemia

Question 4

Features of ascites

Answer 4

• increased fluid shift into space of Disse from intravascular compartment due to increased sinusoidal hydrostatic pressure in portal HTN
• decreased plasma oncotic pressure due to hypoalbuminemia & H2O/Na retention
• increased fluid shift - increased lymphatic drainage from liver - overwhelms thoracic duct capacity - perlocation of hepatic lymph into peritoneal cavity

Question 5

Formation of porto-systemic shunts

Answer 5

• increased portal venous pressures - dilation of anastomotic channels between portal & systemic veins - collateral flow of portal blood into systemic veins
• shunting exacerbates other problems eg hyperammonemia
• periumbilical + superficial abdo - caput medusae
• gastric + lower esophageal - esophageal varices - rupture - potentially fatal hematemesis
• sup rectal & inf rectal - hemorrhoids