Fig. 9
From: Blood finds a way: pictorial review of thoracic collateral vessels
Blockage of the SVC above the azygos vein. a Schematic image of a SVC obstruction above the level of the azygos vein and pathway for collateral flow. b Axial CT image of a 46-year-old male with squamous cell carcinoma (asterisk) causing SVC compression (white arrow) above the azygos vein due to extrinsic mass effect. c Axial CT image showing a dilated azygos vein (gray arrow) entering into the SVC below the blockage. d Axial CT image shows contrast enhancement of the SVC downstream of the blockage (white arrow); the dilated azygos vein is also seen (gray arrow)