Vena caval occlusion after Simon nitinol filter placement: identification with MR imaging in patients with malignancy.

The prevalence of inferior vena caval occlusion associated with the Simon nitinol filter (SNF) was studied at two institutions in the follow-up of filters placed over a 13-month period. Twenty-four consecutive patients with defined indications (contraindication to anticoagulation with pulmonary embolism or deep venous thrombosis [DVT], recurrent pulmonary embolism despite anticoagulation, or extensive DVT [eg, iliofemoral]) underwent placement of a SNF. This patient group includes a high proportion with pelvic or renal malignancy (54%, 13 of 24) or a history of other malignancy. Of these 24, physical examination at follow-up identified 10 symptomatic patients with unilateral or bilateral leg swelling. Of these 10, magnetic resonance imaging, with spin-echo and gradient-echo techniques, demonstrated IVC occlusion in five patients (50%). These data suggest that vena caval occlusion following SNF placement occurs more commonly than previously recognized. Possible contributing factors include reduced venous inflow in patients with prior nephrectomy or pelvic neoplasms, pelvic venous compression by tumor mass, and hypercoagulable states.