Bird's nest filter placement within an enlarged hemiazygos vein for prevention of pulmonary embolism.

Thrombosis of the inferior vena cava (IVC) may result in considerable enlargement of paravertebral, azygos, and hemiazygos collateral veins that may in turn serve as pathways for thromboemboli to the pulmonary circulation. Herein we describe the transfemoral placement of a Bird's Nest filter within an enlarged hemiazygos vein to provide prophylaxis against pulmonary embolism in a patient with right femoral venous thrombosis who could not tolerate systemic anticoagulation. There had been earlier transjugular placement of a Greenfield filter within the suprarenal IVC.