Transient thoracic venous collaterals: an incidental CT finding.

Four patients exhibited thoracic venous collateral circulation on CT of the chest. No clinical or CT evidence of venous obstruction was seen. Repeat CT in one patient following repositioning of the arms from hyperabducted to the anatomic position showed absence of collateral circulation. It appears that hyperabduction of the arms during performance of chest CT can occasionally cause transient obstruction of the subclavian vein and opacification of collateral venous channels.