Collateral pathways observed by radionuclide superior cavography in 70 patients with superior vena caval obstruction.

Schematic representations of collateral pathways that have developed in association with superior vena caval obstruction have been established in studies using radionuclide superior cavography (RNSC). However, these were hampered by the poor resolution of earlier scintillation cameras. Using a modern scintillation camera, we performed RNSC in 70 patients with obstruction of the superior vena caval system, and examined the differences in collateral pathways in the presence or absence of obstruction of the azygos vein. RNSC visualized the site of obstruction and collateral pathways far more readily than in prior studies. When the orifice of the azygos vein was not obstructed, collateral flow drained into the azygos system. When it was obstructed, however, the collaterals drained into the inferior vena caval system. An important collateral pathway comprising the contralateral brachiocephalic vein and the jugular venous arch was also found, which has not previously been reported. Our diagrams of collateral circulation may provide a means of determining the site of obstruction in the superior vena caval system by RNSC.