Portal Vein Occlusion

 Color Doppler US initially: Highly accurate and cost effective


image CT or MR: Complete evaluation and to search for cause





TOP DIFFERENTIAL DIAGNOSES




• Streaming artifact

• Extrinsic compression

• Budd-Chiari syndrome


PATHOLOGY




• Most often associated with hepatic cirrhosis and pancreatitis

• Primary PV thrombosis may be 1st sign of hypercoagulable (prothrombotic) condition


CLINICAL ISSUES




• PV tumor invasion (usually from hepatocellular carcinoma) is associated with poor clinical outcome

• Primary PV thrombosis may mimic cirrhosis
image Results in dysmorphic and malfunctioning liver

• Treatment: Anticoagulation for acute bland thrombosis or hypercoagulable condition
image Add antibiotics for septic thrombophlebitis


DIAGNOSTIC CHECKLIST




• Tumor thrombus expands lumen, enhances, and is contiguous with parenchymal mass

• Thrombosis or fibrosis of extrahepatic portal vein may complicate or preclude liver transplantation

image
(Left) Axial CECT in a 55-year-old man with hepatitis B who presented for routine CT screening to rule out HCC shows cavernous transformation of the portal vein with numerous small collateral veins image in the porta hepatis and hepatoduodenal ligament. The main portal vein cannot be identified.


image
(Right) CT through the porta hepatis in the same patient reveals no normal portal vein branches, only innumerable tiny collateral veins image, diagnostic of cavernous transformation and chronic portal vein occlusion.

image
(Left) Longitudinal grayscale ultrasound image obtained through the porta hepatis in a 51-year-old woman presenting with vague RUQ pain and a recent elevation of liver function tests reveals no apparent abnormalities of the portal vein image.


image
(Right) Longitudinal power Doppler ultrasound obtained in the same patient in the same field of view reveals an acute thrombosis image of the portal vein with a complete absence of flow, which was undetectable with grayscale sonography alone.


TERMINOLOGY


Synonyms




• Portal vein thrombosis (PVT)


Definitions




• Acute, chronic, or neoplastic occlusion of portal vein (PV) due to thrombosis or tumor invasion

• Chronic PV occlusion with numerous periportal collaterals is referred to as “cavernous transformation”


IMAGING


General Features




• Best diagnostic clue
image Low-attenuation thrombus in PV on CECT

image On MR and power Doppler
– Absence of blood flow or flow void in PV
image May be caused by slow flow in portal hypertension

– Nonvisualization of PV (chronic occlusion)

– Cavernous transformation of PV (collateralization in porta hepatis)

• Location
image May involve any portion of intra- or extrahepatic PV


CT Findings




• CECT of acute thrombosis
image Arterial phase (25-40 seconds post bolus injection)
– High attenuation within involved hepatic lobe or segment due to arterioportal shunting
image Transient hepatic attenuation difference (THAD)

image Venous phase (60-70 seconds post bolus injection)
– Equilibration of hepatic contrast enhancement

– Visualization of low-density thrombus

image Nonocclusive thrombosis: Low-density thrombus partially filling PV lumen

image Occlusive thrombosis: Low-density thrombus filling PV lumen
– Extent variable: May include major intrahepatic branches, splenic vein, superior mesenteric vein (SMV)

– Congested (nonoccluded) mesenteric veins upstream from thrombus, mesenteric edema, bowel wall thickening from venous congestion

– Ileus, ascites, and splenomegaly may be seen

• CECT of chronic PV thrombosis
image Chronic occlusion (cavernous transformation) of PV
– Numerous periportal collateral veins along usual course of PV

– Peripancreatic and gallbladder wall varices are common

image Nonvisualization of PV &/or splenic vein
– Thrombosed vein becomes fibrotic “cord” not visible on imaging

image Well-developed portosystemic collaterals
– e.g., splenorenal shunt; esophageal, periumbilical varices

image Associated findings
– Splenomegaly

– Atrophy/hypertrophy complex
image Usual pattern is hypertrophy of central (deep) segments, atrophy of peripheral segments

image May impart lobulated or rounded contour to liver

– Increased hepatic artery size &/or flow

• CECT of PV tumor invasion
image Lumen of vein may be expanded by thrombus
– Main PV > 23 mm diameter

image Variable degree of contrast enhancement of intraluminal tumor thrombus
– Linear enhancing “threads and streaks”
image Best seen on arterial phase of biphasic CECT

– Primary tumor usually visible in hepatic parenchyma or pancreas, often in direct contiguity with thrombus

– Commonly seen in hepatocellular carcinoma

– Less common in pancreatic carcinoma, cholangiocarcinoma, endocrine tumor of pancreas, metastases


MR Findings




• T1WI
image High-signal filling defect

• T2WI
image High-signal acute or tumor thrombus

• T2* GRE
image PV tumor enhances avidly, especially on GRE sequences

• T1WI C+ FS
image Liver parenchyma supplied by thrombosed veins may enhance avidly in arterial phase due to increased hepatic artery flow
– Transient hepatic intensity difference (THID)

image Subacute thrombus hyperintense on T1 and T2 due to methemoglobin

image Tumor thrombus on enhanced MR
– Analogous to CECT (expanded lumen, enhancing thrombus, contiguous with tumor)

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Nov 16, 2016 | Posted by in GASTROINTESTINAL IMAGING | Comments Off on Portal Vein Occlusion

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