Inferior vena cava "birds nest" filters--2 year follow-up.

This study examines long term efficacy and saftey of "birds nest" filters (Cook), and the use of doppler ultrasound to assess patency. Of the seventeen "birds nest" filters inserted twelve were available for study. All patients were reviewed for evidence of recurrent pulmonary emboli or filter complication. Mean length of follow up was 10 months, (7 had follow up of > 12 months). Three have had further episodes of deep venous thrombosis, with probable recurrent pulmonary embolism in one. No patient had evidence of thrombosis of the inferior vena cava. No fracture or migration of the "birds nest" filters was found. Ten of the twelve filters studied with ultrasound could be visualized within the cava. In all, turbulent flow was detected with colour and duplex doppler study. We conclude that insertion and use of the "birds nest" filters is safe, with a high long term patency rate and few initial or long term complications. Doppler ultrasound is a simple and rapid method of assessing venous patency.