Objective: The aim of this prospective study was to assess the advantages and limitations of various imaging techniques in identifying problems associated with percutaneous placement of filters in the inferior vena cava.
Subjects and methods: One hundred four vena caval filters (65 Filcard, 39 Cardial) were placed in 100 patients (four patients received two filters). Venacavograms, duplex sonograms of the abdomen, abdominal radiographs, perfusion scans of the lung, and impedance plethysmograms were obtained in all patients within 1-2 days and 3 months after filter placement. CT scans of the filter were obtained in 55 patients.
Results: In five patients, thrombosis of the inferior vena cava, with retraction of the filter struts in four patients, was noted on venacavograms, CT scans, duplex sonograms, and impedance plethysmograms. Perforation of the inferior vena cava was noted in 36 patients after comparison of findings on venacavograms and CT scans, with an increase in the filter span in 29 patients (apparent on duplex sonograms in only two patients). Four filter tiltings (> 30 degrees) and 25 migrations (> 5 mm) were noted on abdominal radiographs. Trapped thrombi in the filter were shown on venacavograms in nine cases, but on duplex sonograms and unenhanced CT scans in only two cases.
Conclusion: Our study shows that the major complications of inferior vena caval filters can be detected by noninvasive examinations. Only venacavograms consistently show small trapped thrombi that do not extend above the filter, but the importance of such thrombi is unknown.