Transparavertebral Occlusion of a Large Venovenous Collateral in a Fontan Patient.

Patients with a univentricular heart following completion of the Fontan circulation often experience varying degrees of desaturation due to the formation of venovenous collaterals. We present a rare case of a Fontan patient with an enlarged azygous vein shunting into the pulmonary venous system, causing significant desaturation. As no standard access site provided a viable pathway for standard interventional occlusion, we opted for an ultrasound-guided direct puncture at the level of the 12th thoracic vertebra with the patient in the prone position. The azygous vein was accessed via a dilated external vertebral venous plexus and successfully occluded using a vascular plug. This access technique expands the interventional options available for patients with complex anatomies or occluded conventional access site vessels.