Definition: Obstruction of PV due to thrombosis

Absent blood flow within PV on color or spectral Doppler

Cavernous transformation of PV: Multiple portal venous collaterals develop anterior to thrombosed PV

May see hypertrophied and high-velocity hepatic artery, which compensates for thrombosed PV

CECT/MR

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  Comprehensive evaluation: Extent of occlusion and collateralization

  
  
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  Search for etiology and underlying condition

Hepatic vein/inferior vena cava occlusion

Nonocclusive thrombosis

False-positive PV occlusion

False-negative PV occlusion

Tumor in vein (tumor thrombus)

Splenic vein occlusion

Dilated bile duct

Etiology

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  Thrombosis due to flow stasis, hypercoagulability, intraabdominal inflammation

  
  
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  Tumor in vein (formerly referred to as tumor thrombus) or direct tumor invasion

Acute thrombosis

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  Lumen filled with thrombus, diameter may be enlarged

Chronic thrombosis

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  Thrombosis accompanied by cavernous transformation (collateralization in porta hepatis)

Techniques to differentiate very slow flow vs. thrombus: Decrease color box width; place color focus position at or below vessel; decrease scale (PRF); increase color gain; increase color write priority; try B-flow mode; decrease wall filter; push on belly to propel portal venous blood

Grayscale cine of PV (without moving transducer) may show slow flow not detectable with color Doppler

Blooming on color Doppler may obscure small thrombus