What are the diagnostic criteria for portal vein thrombosis?

Diagnostic Criteria for Portal Vein Thrombosis

Doppler ultrasound is the mandatory first-line diagnostic test for portal vein thrombosis, followed immediately by contrast-enhanced CT scan in the portal venous phase for confirmation and complete characterization. 1, 2, 3, 4

Initial Imaging Approach

Doppler ultrasound findings diagnostic of PVT include:

• Absence of flow within the portal vein lumen 2, 3, 4
• Hyperechoic thrombus visible within the portal vein 2, 3, 4
• Flow reversal within the portal system (100% specific for clinically significant portal hypertension) 2, 3

Proceed immediately to contrast-enhanced CT scan for:

• Definitive diagnostic confirmation 2, 3, 4
• Assessment of thrombus extension to mesenteric and splenic veins 2, 3, 4
• Identification of local causative factors (malignancy, pancreatitis, inflammatory conditions) 2, 3
• Detection of bowel ischemia or congestion 2, 3, 4

Critical technical consideration: Images must be acquired during the portal venous phase, not late arterial phase, as low portal flow can cause delayed contrast arrival creating false-positive appearances of thrombosis. 4

Distinguishing Acute from Chronic PVT

Acute thrombosis is characterized by:

• Clinical presentation with abdominal pain (present in 90% of cases) 1
• Systemic inflammatory response syndrome (present in 85% of cases) 1
• Spontaneous hyperdense clot visible in portal vein lumen on non-enhanced CT 2, 3, 4
• Absence of portal cavernoma formation 2, 3, 4

Chronic thrombosis demonstrates:

• Presence of portal cavernoma (collateral venous channels) 2, 3
• Absence of acute inflammatory symptoms 1

Differentiating Benign Thrombus from Malignant Portal Vein Invasion

This distinction has critical prognostic and therapeutic implications. Two imaging findings are highly specific for tumorous portal vein invasion rather than bland thrombosis:

• Arterial phase hyperenhancement (APHE) within the thrombus 1, 3
• High signal intensity within the obstructed vessel on diffusion-weighted MRI with high b-values 1, 3

Assessment of Complications

Evaluate for intestinal ischemia using these criteria:

• Persistent severe abdominal pain despite anticoagulation 2, 4
• Organ failure 2, 4
• Massive ascites or rectal bleeding 2, 4
• CT findings: distal mesenteric thrombosis, bowel wall abnormalities, mesenteric stranding, pneumatosis intestinalis, or portal venous gas 4

Characterization Requirements

Complete diagnostic assessment must determine:

• Whether occlusion is partial or complete 2
• Which vessels are involved (main portal vein, right/left branches, mesenteric, splenic) 1, 2
• Presence of ascites (visible in 50% of acute cases on imaging) 1

Follow-Up Imaging Protocol

Structured surveillance includes:

• CT scan at 6-12 months to assess portal venous system recanalization 2, 3, 4
• Doppler ultrasound early after diagnosis, then every 6 months for ongoing surveillance 2, 3
• Screening for gastroesophageal varices in patients with persistent occlusion 2, 3, 4

Additional Diagnostic Tools

In patients with compensated advanced chronic liver disease:

• Liver stiffness measurement by transient elastography with cut-off >20-25 kPa can diagnose clinically significant portal hypertension 2
• LSPS score (liver stiffness × spleen size/platelet count) >2.06 has 90% specificity for portal hypertension 2

Common pitfall: Do not rely solely on ultrasound for complete characterization—CT or MRI is essential to assess extent, identify underlying causes, and detect complications that directly impact mortality and morbidity. 1, 2, 3