Portal Hypertension, Idiopathic Noncirrhotic

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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.