What is the diagnostic approach for portal vein thrombosis?

Diagnostic Approach for Portal Vein Thrombosis

Doppler ultrasound should be used as the first-line investigation for diagnosing portal vein thrombosis, followed by contrast-enhanced CT scan in the portal phase for confirmation and assessment of extension. 1

Initial Diagnostic Workup

• Doppler ultrasound is the first imaging procedure of choice when portal vein thrombosis is suspected, looking specifically for:

  • Absence of flow within the portal vein
  • Hyperechoic thrombus in the portal lumen
  • Flow reversal within the portal system (100% specific for clinically significant portal hypertension) 1, 2
  • Presence of portosystemic collaterals (100% specific for clinically significant portal hypertension) 2

• Contrast-enhanced CT scan should be performed to:

  • Confirm the diagnosis
  • Assess extension of thrombus to mesenteric veins and arches
  • Identify presence of local factors
  • Evaluate for signs of bowel congestion and ischemia 1
  • Note: Images acquired during late arterial phase are not optimal for portal vein thrombosis diagnosis 1

Characterization of Portal Vein Thrombosis

• Recent thrombus can be identified by:

  • Clinical presentation with abdominal pain and/or systemic inflammatory response syndrome
  • Spontaneous hyperdense clot in portal vein lumen on non-enhanced CT
  • Absence of portal cavernoma 1

• Assessment should determine:

  • Whether thrombosis is partial or complete
  • Which vessels are involved (portal vein, superior mesenteric vein, splenic vein) 3
  • Signs of intestinal ischemia (persistent severe abdominal pain despite anticoagulation, organ failure, massive ascites, rectal bleeding) 1

Additional Diagnostic Considerations

• Splenomegaly is sensitive for portal hypertension but nonspecific when used alone 2

• Portal vein parameters to evaluate include:

  • Portal vein diameter
  • Flow velocity
  • Congestion index (combination of portal vein diameter and velocity) 2

• Liver stiffness measurement by transient elastography with a cut-off of >20-25 kPa can help diagnose clinically significant portal hypertension in patients with compensated advanced chronic liver disease 2

• Combined parameters such as LSPS score (liver stiffness × spleen size/platelet count) can improve diagnostic accuracy, with a score >2.06 having 90% specificity 2

Differential Diagnosis

• The main differential diagnosis of portal vein thrombosis is:
  • Malignant portal vein invasion (most frequently by hepatocellular carcinoma)
  • Portal vein constriction (typically by pancreatic cancer or cholangiocarcinoma) 4
  • MRI with hepato-specific contrast injection is recommended to detect/characterize nodules prior to planned intervention for Budd-Chiari syndrome 5

Follow-up Imaging

• Follow-up CT scan should be performed at 6-12 months to assess recanalization of the portal venous system 1
• Doppler ultrasound should be performed early and then every 6 months to detect thrombosis or TIPS dysfunction in patients with Budd-Chiari syndrome or chronic portal vein thrombosis 5
• Screening for gastroesophageal varices is recommended in unrecanalised patients 1

Common Pitfalls to Avoid

• Low portal vein flow can cause delayed contrast arrival, creating a false positive appearance of thrombosis on CT 1
• Relying solely on splenomegaly for diagnosis without additional parameters 2
• Failing to screen for underlying causes of portal vein thrombosis, such as cirrhosis, hepatobiliary malignancy, inflammatory abdominal disease, or myeloproliferative disorders 4
• Not considering portal vein thrombosis in patients with unexplained abdominal pain or signs of portal hypertension 6

By following this diagnostic algorithm, clinicians can effectively diagnose portal vein thrombosis and guide appropriate management decisions.