Portal vein thrombosis
Reduced portal flow velocity (stasis)
Vascular injury
Tumor thrombosis
Extrinsic compression by mass or fibrogenic lesions
Congenital vascular anomalies
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Intrahepatic
Propagation of large portal vein thrombosis or emboli
Diseases that affect small portal veins
Specific etiology may not be identifiable
Clinical Issues
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5-10% in patients with portal hypertension in developed countries
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Sequelae depend on location, cause, time course, and extent of blockage
Microscopic
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Often inconsistent or irregularly distributed, may be missed in biopsy specimens
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Subtle alterations of portal venules
Dilated portal venules
Multiple collateral venules
Herniation of portal venules into parenchyma
Obliteration of portal venules, similar to hepatoportal sclerosis, may be seen
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Infarcts of Zahn
Persistent occlusion can lead to atrophy of entire segments of liver
True infarcts rarely develop
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Nodular regenerative hyperplasia may be seen
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Findings suggestive of underlying etiologies
in the hilar region. Propagation into smaller intrahepatic portal veins 
is also grossly noticed.
in the setting of portal vein thrombosis. Note the presence of fibrin thrombus in the lumen.
in compressed portal stroma.
are present in this portal tract in a case of portal venous obstruction indicating elevated portal pressures.
