Thoracic arteriovenous fistula: venous connection to right iliac vein.

A 5-year-old boy had clinical, cardiac catheterization, and operative findings of a thoracic arteriovenous fistula arising from the right subclavian artery. The venous connection was to the paravertebral plexus with eventual drainage into the inferior vena cava through the right common iliac vein. To our knowledge, this type of fistula has not been reported previously and is believed to represent embryological defects of the first or second posterior intercostal arteries as well as maldevelopment of the venous connections of azygos vein to the superior vena cava, which resulted in the observed caudal venous pathways becoming operative.