Portal Hypertension

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Definition of portal hypertension (pHTN): an increase in the portal-caval venous pressure gradient >5 mm Hg
  • pHTN is the result of blood flow obstruction through the portal venous system at the prehepatic, hepatic (sinusoidal), or posthepatic level.
  • Gastroesophageal varices develop when the portal systemic gradient is >10 mm Hg.
  • A gradient >12 mm Hg is a predictor of variceal hemorrhage.
  • Children may develop complications at lower gradients than adults.
  • A major cause of morbidity and mortality in children with chronic liver disease

ETIOLOGY

  • pHTN can be caused by cirrhosis or noncirrhotic causes.
    • Hepatocellular disorders that can result in cirrhosis include chronic viral hepatitis (hepatitis B and C), autoimmune hepatitis, α1-antitrypsin deficiency, Wilson disease, glycogen storage disease, and schistosomiasis.
    • Biliary disorders that can result in cirrhosis include biliary atresia, progressive familial intrahepatic cholestasis, primary sclerosing cholangitis (PSC), ductal plate malformation/congenital hepatic fibrosis, and choledochal cyst.
  • Noncirrhotic pHTN (NCPH) can be classified as prehepatic, intrahepatic, and posthepatic.
    • Prehepatic causes include portal vein thrombosis (PVT; increased risk with umbilical vein catheterization, sepsis, dehydration, and hypercoagulable state), extrinsic compression of the portal vein, splenic vein thrombosis, or AV fistula.
    • Posthepatic causes include Budd-Chiari syndrome, occlusion of hepatic veins or retrohepatic inferior vena cava, constrictive pericarditis or right heart failure, or severe tricuspid regurgitation.
    • Intrahepatic causes can be subclassified as presinusoidal, sinusoidal, or postsinusoidal.
      • Presinusoidal causes include PSC, sarcoidosis, congenital hepatic fibrosis, or schistosomiasis.
      • Sinusoidal causes include nodular regenerative hyperplasia.
      • Postsinusoidal cause includes sinusoidal obstruction syndrome.

PATHOPHYSIOLOGY

  • pHTN occurs in the setting of hemodynamic changes that lead to increased resistance to portal venous flow by intrahepatic vasoconstriction, mechanical obstruction, and increased portal flow.
  • Mechanical factors include regenerative nodules, fibrotic bands, and hepatocyte swelling.
  • Hemodynamic changes occur due to increased production of vasoconstrictors (i.e., endothelins, angiotensin II, and thromboxane A2) and a decrease in endothelial vasodilators (i.e., nitric oxide) resulting in sinusoidal constriction.
  • Splanchnic blood flow increases due to release of vasodilators (including vascular endothelial growth factor [VEGF] and nitric oxide [NO]) resulting in splanchnic arteriolar vasodilation.
    • The effect is systemic hypotension, expanded intravascular volume, and increased cardiac output.
  • pHTN results in the development of portosystemic collaterals, splenomegaly, and thrombocytopenia.

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