Vena cava duplex imaging before caval interruption

Purpose: Venacavograms are routinely obtained before vena cava filter placement to evaluate cava size, patency, and the presence of thrombus or venous anomalies. The objective of this study was to determine the ability of duplex ultrasonography to adequately evaluate the inferior vena cava (NC) for size, patency, and the presence of thrombus before Greenfield filter (GF) insertion. Methods: Duplex ultrasonographic scans were performed in 40 patients who had documented lower-extremity deep venous thrombosis diagnosed by duplex scan before GF placement. The infrarenal transverse and anteroposterior diameters of the NC were measured, and the entire IVC was imaged for patency and the presence of thrombus or anomalies. Preoperative venacavograms were not obtained in any patients who had GFs placed in the operating room, but was performed during surgery during filter insertion. An additional 26 patients who had deep venous thrombosis and did not have caval interruption underwent NC duplex to determine the patency and proximal extent of venous thrombosis. Results: The indications for GF placement were contraindication to anticoagulation in 72.5% (29 patients); five filters were placed prophylactically; three for failure of anticoagulation; two after a complication of anticoagulation; and one before pulmonary embolectomy. The filters were placed in the operating room by surgeons in 82.5% of patients, with the remainder inserted in an angiography suite by an interventional radiologist. The ability of duplex to measure a transverse diameter of 26 mm or less had a sensitivity of 97.5%, positive predictive value of 100%, and overall accuracy of 97.5% using venacavography as the standard. Measurements of IVC diameter by duplex correlated with those based on venacavograms (r = 0.766; p < 0.001). Of the entire group of 66 IVC duplex examinations, one (1.5%) was incomplete because of technical limitations. IVC thrombus was noted by duplex in two patients who underwent GP insertion, which was confirmed with venacavography: No IVC anomalies were noted by duplex scans or venacavograms. Conclusion: Duplex ultrasonography is a useful and accurate method for assessment of the IVC before vena cava filter placement.