Simon nitinol filter

The incidence of inferior vena cava (IVC) thrombosis associated with the Simon Nitinol filter was reviewed at two institutions in 20 patients with lower- extremity deep venous thrombosis within 12 months. Ten patients had underlying malignancy. Clinical findings were correlated with findings of color-flow US, spin-echo (SE) MR imaging, and gradient-echo (GE) MR imaging of the IVC. Four of the 20 patients developed symptoms of IVC thrombosis (bilateral leg edema) within 5 weeks. MR imaging in all four documented IVC thrombosis (absence of intracaval flow void on SE images, absence of increased signal on GE images), and each had underlying malignancy (three pelvic tumors, one renal cell carcinoma). The authors conclude that patients with tumors, especially genitourinary primary tumors, may be at increased risk of IVC thrombosis in the presence of this filter, possibly because of pelvic venous compression or reduced renal vein inflow with prior nephrectomy; MR imaging is very useful for following IVC patency