How do you diagnose Portal Vein (PV) thrombosis?

Diagnosis of 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

Diagnostic Algorithm

Initial Imaging

• Doppler ultrasound is the first imaging procedure of choice when PVT is suspected 1
  • Look for absence of flow within the portal vein 1
  • Hyperechoic thrombus in the portal lumen may be present but can sometimes be lacking 1
  • Has a 98% negative predictive value 2
  • Note: Doppler ultrasound is operator-dependent and has lower sensitivity than CT imaging 1

Confirmatory Imaging

• Contrast-enhanced CT scan should be used to confirm diagnosis and assess extension 1
  • Must be performed during the portal phase to avoid false positives 1
  • Portal phase CT shows absence of visible lumen corresponding to the portal vein clot 1
  • Provides critical information about:
    • Extent of thrombus to mesenteric veins and arches 1
    • Presence of local factors 1
    • Signs of bowel congestion and ischemia 1

Alternative/Additional Imaging

• MR imaging can be used as an alternative to CT 1
  • Contrast-enhanced 3D MR angiography provides comparable accuracy to digital subtraction angiography 3
  • Particularly useful for evaluating biliary complications in chronic PVT 1

Important Diagnostic Considerations

Timing of Thrombosis

• Recent thrombus (acute PVT) can be identified by:
  • Clinical presentation with abdominal pain and/or systemic inflammatory response syndrome 1
  • Spontaneous hyperdense clot in portal vein lumen on non-enhanced CT (suggests <30 days from onset) 1
  • Absence of portal cavernoma (although cavernoma may develop as early as 15-30 days after onset) 1

Pitfalls to Avoid

• Images acquired during late arterial phase are not optimal for PVT diagnosis 1
• Low portal vein flow can cause delayed contrast arrival, creating a false positive appearance of thrombosis 1
• Acute thrombosis may superimpose on long-standing cavernoma, complicating diagnosis 1

Differential Diagnosis

• Malignant portal vein invasion (especially by hepatocellular carcinoma) 4
• Portal vein constriction (typically by pancreatic cancer or cholangiocarcinoma) 4
• Underlying cirrhosis or obliterative portal venopathy must be established or ruled out 1

Evaluating Complications

• Signs suggestive of intestinal infarction (most concerning complication) include:
  • Persisting severe abdominal pain despite anticoagulation 1
  • Organ failure (shock, renal failure, metabolic acidosis, elevated arterial lactates) 1
  • Massive ascites and rectal bleeding 1
  • CT findings: distal thrombosis, bowel wall abnormalities, mesenteric stranding, pneumatosis, and portal venous gas 1

Follow-up Imaging

• Perform CT scan at 6-12 months to assess recanalisation of the portal venous system 1
• Screen for gastroesophageal varices in unrecanalised patients 1
• Perform MR imaging cholangiography in patients with persisting cholestasis or biliary tract abnormalities suggestive of portal biliopathy 1

Underlying Causes

• All patients should be investigated for thrombophilic conditions 5
• Common causes include cirrhosis, hepatobiliary malignancy, abdominal infectious/inflammatory diseases, and myeloproliferative disorders 4, 5

By following this diagnostic approach, clinicians can accurately diagnose portal vein thrombosis, assess its extent, identify complications, and guide appropriate treatment decisions to reduce morbidity and mortality.