A patient with superior vena cava obstruction undergoes CT chest with contrast. Which CT finding most reliably indicates SVC occlusion rather than stenosis?
- A Filling defect with complete non-opacification of the SVC with collateral venous channels ✓
- B Opacification delay in the SVC during arterial phase
- C Increased calibre of the azygos vein alone
- D Mediastinal widening on plain X-ray
Correct answer: A. Filling defect with complete non-opacification of the SVC with collateral venous channels
Explanation
Complete SVC occlusion is demonstrated on CT venography or contrast-enhanced CT as total non-opacification of the SVC lumen with visible thrombus or tumour and prominent collateral venous pathways (azygos, hemiazygos, internal mammary, lateral thoracic veins). A filling defect without complete occlusion, or opacification delay, suggests high-grade stenosis rather than complete occlusion. Plain X-ray widening is non-specific.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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