What tests should be done to evaluate portal vein and superior mesenteric vein (SMV) thrombosis?

Diagnostic Approach for Portal Vein and Superior Mesenteric Vein Thrombosis

Contrast-enhanced CT angiography (CTA) with arterial and venous phases is the gold standard diagnostic test for evaluating portal vein and superior mesenteric vein thrombosis, offering the highest sensitivity and specificity. 1

Initial Diagnostic Workup

First-Line Imaging

• Doppler Ultrasonography
  • Recommended as initial screening test 2
  • Advantages:
    • Non-invasive, widely available
    • Can detect absence of flow in portal vein
    • Can identify hyperechoic thrombus in portal lumen
    • Can evaluate portosystemic collaterals and flow direction
  • Limitations:
    • Operator-dependent
    • Limited by bowel gas, obesity
    • Lower sensitivity than CT for distal thrombosis 1
    • May miss thrombus in some cases 1

Definitive Imaging

• Contrast-Enhanced CT Angiography (CTA)

  • Essential components:

    1. Pre-contrast phase: Detects vascular calcification and hyperattenuating intravascular thrombus 1
    2. Arterial phase: Evaluates arterial supply
    3. Portal venous phase: Critical for thrombus visualization 1
    4. Multi-planar reconstructions: Assesses vessel origins and extent of thrombosis 1

  • Key findings:

    • Portal vein filling defect or absence of visible lumen
    • Extent of thrombus into mesenteric veins
    • "Target sign" in SMV thrombosis 1
    • Associated findings: bowel wall thickening, pneumatosis, ascites
    • Signs of intestinal ischemia: bowel wall enhancement abnormalities, mesenteric stranding 1

  • Important technical considerations:

    • Timing is crucial - images must be acquired during portal phase
    • Late arterial phase images can lead to false positives 1
    • No oral contrast needed (may delay diagnosis) 1
    • Should be performed despite renal impairment as benefits outweigh risks 1

Alternative/Supplementary Imaging

• MR Venography

  • Useful when:
    • CT contraindicated
    • Biliary complications suspected
    • Radiation exposure concerns
  • Limited use in emergency settings 1

• Conventional Angiography

  • Now primarily reserved for:
    • Equivocal cases at noninvasive imaging 3
    • Planned endovascular intervention 1
    • Therapeutic procedures 4, 5

Diagnostic Indicators of Chronicity

• Acute thrombosis indicators:

  • Symptoms present for ≤8 weeks
  • Spontaneous hyperdense clot on non-enhanced CT 1
  • Absence of portal cavernoma 2

• Chronic thrombosis indicators:

  • Symptoms present for >8 weeks
  • Presence of portal cavernoma (collateral vessels)
  • Cavernoma may develop as early as 15-30 days after symptom onset 1

Additional Diagnostic Workup

• Laboratory testing:
  • Complete blood count
  • Liver function tests
  • Coagulation profile
  • Thrombophilia workup:
    • JAK2V617F mutation
    • Paroxysmal nocturnal hemoglobinuria (PNH)
    • Protein C and S deficiency 2, 6

Common Pitfalls to Avoid

1. Delayed diagnosis: Each 24-hour delay doubles mortality 1
2. Inadequate CT protocol: Missing proper portal venous phase imaging
3. Misinterpreting late arterial phase images: Can lead to false positive diagnosis 1
4. Overlooking superimposed acute thrombosis on chronic cavernoma 1
5. Failing to assess extent of thrombosis: Mesenteric vein involvement significantly increases mortality 2

Follow-up Imaging

• CT scan at 6-12 months to assess recanalization 2
• Screening for gastroesophageal varices in patients without recanalization 2
• Doppler ultrasound every 6 months after TIPS placement, if performed 2

In summary, while Doppler ultrasonography serves as a valuable initial screening tool, contrast-enhanced CT angiography with proper protocol (pre-contrast, arterial and venous phases) remains the definitive test for diagnosing and evaluating the extent of portal vein and superior mesenteric vein thrombosis.