Portal Hypertension, Idiopathic Noncirrhotic

JAVMA paper

• Portal hypertension
• Sustained impairment of forward venous flow anywhere along the path from the portal vein to the right side of the heart.
• Luminal (thrombosis, parasites) or extraluminal obstruction (hepatic fibrosis or nodular regeneration) or relative restriction of flow due to massive portal volume overload (arterioportal fistulas).
• Hepatomegaly associated with posthepatic obstruction
• Microhepatica – associated with prehepatic/hepatic causes.
• Hepatic encephalopathy and GI bleeding not associated with posthepatic causes.
• Most common causes are RHS heart failure and severe diffuse hepatobiliary disease that results in cirrhosis.

Histology

• indistinguishable from microvascular dysplasia or surgically created portosystemic shunts
  • Portal triad arteriole proliferation
  • portal veins small to large
  • variable portal triad fibrosis
  • hepatic lobule size variation
  • arterioles scattered throughout hepatic parenchyma
  • portal veins – small
  • expanded perivenular connective tissue by arterioles and distended lymphatics.