Should a contrast‑enhanced computed tomography (CT) scan be used to evaluate portal vein thrombosis, or is a non‑contrast CT sufficient?

CT Scan for Portal Vein Thrombosis Evaluation

Portal vein thrombosis should be evaluated with contrast-enhanced CT scan in the portal venous phase, not non-contrast CT. 1, 2

Recommended Imaging Protocol

Contrast-enhanced CT in the portal venous phase is the definitive imaging modality for confirming portal vein thrombosis diagnosis, assessing thrombus extension, identifying causative factors, and detecting complications. 1, 2

Initial Screening

• Doppler ultrasound serves as the first-line investigation when portal vein thrombosis is suspected, looking for absence of flow within the portal vein, hyperechoic thrombus in the portal lumen, and flow reversal within the portal system. 1, 2, 3
• Flow reversal within the portal system on Doppler is 100% specific for clinically significant portal hypertension. 1, 3

Confirmatory Imaging with Contrast-Enhanced CT

Proceed immediately to contrast-enhanced CT scan in the portal venous phase for:

• Definitive diagnosis confirmation 1
• Assessment of thrombus extension to mesenteric veins and arches 1, 2
• Identification of local causative factors 1, 2
• Detection of bowel congestion or ischemia 1, 2
• Evaluation for complications 1

Why Non-Contrast CT is Inadequate

Non-contrast CT has extremely limited utility for portal vein thrombosis evaluation and should not be used as the primary diagnostic modality. 4

The only specific finding on non-contrast CT is:

• Spontaneous hyperdense clot in the portal vein lumen, which helps identify acute thrombosis (but this is not reliable for chronic thrombosis). 1, 2, 3

Non-contrast CT cannot:

• Reliably visualize the thrombus in most cases 4
• Assess thrombus extension 1
• Distinguish between bland and malignant thrombus 5
• Evaluate for bowel ischemia or congestion 1, 2

Critical Technical Considerations

Timing of Contrast Phase Matters

Images acquired during late arterial phase are not optimal for portal vein thrombosis diagnosis. 2

Portal venous phase imaging is essential because:

• Low portal vein flow can cause delayed contrast arrival in arterial phase 2
• Arterial phase imaging can create false positive appearance of thrombosis 2
• Portal venous phase provides optimal visualization of the portal venous system 1, 2

Distinguishing Benign from Malignant Thrombus

Contrast-enhanced imaging is critical for characterizing thrombus as benign versus malignant:

• Arterial phase hyperenhancement within the thrombus suggests malignancy 1
• Mean thrombus density on contrast CT reliably distinguishes neoplastic (81.39 HU) from bland (32.88 HU) thrombi 5
• This distinction has major therapeutic implications, as malignant thrombus contraindicates liver resection, transplantation, or transarterial chemoembolization 6

Follow-Up Imaging Protocol

CT scan should be performed at 6-12 months to assess recanalization of the portal venous system. 1, 2, 3

Doppler ultrasound should be used:

• Early after diagnosis 1
• Every 6 months for ongoing surveillance 1, 3

Screen for gastroesophageal varices in patients with persistent occlusion. 1, 2, 3

Common Pitfalls to Avoid

• Do not rely on non-contrast CT alone – it will miss most cases and cannot assess extension or complications 4
• Avoid arterial phase-only imaging – this can lead to false positives due to delayed contrast arrival 2
• Do not skip contrast in patients with renal insufficiency when portal vein thrombosis is suspected – the diagnostic benefit generally outweighs the risk, similar to principles in acute mesenteric ischemia 4
• Recognize that peripheral portal vein enhancement is nonspecific and associated with underlying endothelial injury, not diagnostic of thrombosis alone 7