From the Guidelines
Duplex ultrasound is the recommended first-line imaging modality for diagnosing portal vein thrombosis. This non-invasive test combines traditional B-mode ultrasound with Doppler flow assessment, allowing visualization of both the thrombus and evaluation of blood flow dynamics in the portal venous system 1. When performing a duplex ultrasound for suspected portal vein thrombosis, the sonographer should thoroughly examine the main portal vein and its branches, looking for echogenic material within the vessel lumen and absence of Doppler flow signals.
Key aspects of the duplex ultrasound examination include:
- Thorough examination of the main portal vein and its branches
- Assessment of collateral vessels, which may develop as a compensatory mechanism
- Use of color Doppler to identify areas of absent flow
- Use of spectral Doppler to detect alterations in flow velocity and direction
- Patients should fast for 6-8 hours before the procedure to reduce bowel gas and optimize visualization
The advantages of duplex ultrasound for diagnosing portal vein thrombosis include:
- Avoidance of radiation exposure and contrast agents
- Ability to perform the procedure at bedside for critically ill patients
- Allowance for serial monitoring of thrombus evolution or resolution during treatment
- Non-invasive nature of the test
However, if ultrasound results are inconclusive or if more detailed anatomical information is needed, CT angiography or MR venography may be required as follow-up imaging studies 1.
From the Research
Diagnosis of Portal Vein Thrombus
- Duplex sonography is a reliable method for diagnosing portal vein thrombosis, as it can demonstrate abnormal vascular structures and flow patterns 2.
- Duplex ultrasound allows direct access to portal venous and hepatic vein hemodynamics, making it a valuable tool for detecting portal and splenic venous thrombosis 3.
- The use of contrast-enhanced sonography can help differentiate between benign and malignant portal vein thrombosis, with high sensitivity and specificity 4.
Characterization of Portal Vein Thrombus
- Contrast-enhanced sonography can be used to characterize the nature of a thrombus, with pulsatile flow in the thrombus on power Doppler sonography and positive enhancement of the thrombus on contrast-enhanced sonography indicating a malignant thrombus 4.
- Magnetic resonance noncontrast thrombus imaging (MR-NCTI) sequences, such as 3D T1 TFE and 3D T1 Dixon FFE, can be used to differentiate acute from chronic portal vein thrombosis 5.
Treatment and Management
- Recanalization using local methods is recommended for symptomatic non-cavernomatous portal vein thrombosis, while anticoagulation alone may be sufficient for non-cirrhotic patients with recent portal vein thrombosis 6.
- Implantation of transjugular intrahepatic portosystemic shunt can be helpful in cirrhotic patients with non-cavernomatous portal vein thrombosis to reduce portal pressure and diminish the risk of re-thrombosis 6.