Utility of duplex ultrasound in the diagnosis of asymptomatic catheter-induced subclavian vein thrombosis.

Asymptomatic thrombosis of the subclavian vein is common after placement of indwelling catheters. The sequelae of these thrombi are not known. Investigation is hampered by the requirement for venography for diagnosis; consequently, a noninvasive method of diagnosis would be welcome in this context. We have studied prospectively 32 subclavian catheters to determine the usefulness of duplex ultrasound in diagnosing asymptomatic thrombosis. Sixteen arm venograms were normal and all gave normal duplex scans. No false-positive scans were obtained. Eleven venograms demonstrated nonocclusive mural thrombi. Only three of these were seen with duplex ultrasound. Five totally occlusive thrombi were seen on venography, of which only two were detected with duplex sonography. The three thrombi not found with duplex ultrasound were short proximal venous occlusions. The insensitivity of this technique to asymptomatic subclavian thrombi limits its usefulness as a screening tool.