Detection of Extensive Inferior Vena Cava Filter Thrombus with Bedside Ultrasound

Introduction Presented here is a case of an inferior vena cava (IVC) filter thrombus detected on bedside ultrasound (US) of the proximal IVC. Case A 44 year old woman with a history of two unprovoked pulmonary emboli (PE)... [ view full abstract ]

Introduction
Presented here is a case of an inferior vena cava (IVC) filter thrombus detected on bedside ultrasound (US) of the proximal IVC.

Case
A 44 year old woman with a history of two unprovoked pulmonary emboli (PE) secondary to lower extremity deep vein thrombi (DVT), inferior vena cava filter placement four years prior to admission, and uterine leiomyoma with history of menorrhagia presented to the emergency room with complaints of painful right lower extremity swelling, presyncope, and dyspnea on exertion for the one week. She endorsed noncompliance with anticoagulation (rivaroxaban) and menorrhagia.

In the emergency room the patient was tachycardic to 130s but otherwise hemodynamically stable. Physical exam revealed right lower extremity tenderness and swelling of the calf and thigh. Labs were significant for a microcytic anemia with hemoglobin of 5.7 and mean corpuscular volume (MCV) of 64. International normalized ratio (INR) was 1.2. Right lower extremity duplex revealed thrombi within the femoral and popliteal veins. CT angiography was suspicious for small peripheral left lower lobe filling defects (figure 1). The patient was diagnosed with acute DVT with suspected PE and symptomatic anemia secondary to menorrhagia and admitted to the medical intensive care unit.

Bedside inferior vena cava ultrasonography was preformed to evaluate fluid status, during which the patient was noted to have a near-completely occlusive, hyperechoic, IVC mass extending inferiorly from the cavo-atrial junction (figure 2). These US findings lead to immediate changes in management, including further imaging that was not previously considered. Computed tomography (CT) angiography of the abdomen and pelvis delineated extension of the right femoral and popliteal thrombus to involve the IVC filter and proximal IVC to the level of the cavo-atrial junction (figure 3).

The patient was managed on an intravenous heparin drip. Vascular surgery was consulted and the patient taken for bilateral lower extremity and iliocaval thrombolysis with recanalization of the vena cava. She will continue lifelong anticoagulation.

Discussion
Placement of an inferior vena cava filter used in conjunction with anticoagulation has been shown to reduce the risk of pulmonary embolus in patients who present with deep vein thrombus. Unfortunately, IVC filters have also been associated with an increased risk of recurrent deep venous thrombosis and inferior vena cava occlusion.

Occlusion of IVC filters due to thrombus formation has been shown to occur from between 5 – 30 percent of patients, with propagation occurring both superiorly and inferiorly from the filter. Most often IVC filter thrombosis is directly detected using contrast enhanced computed tomography angiography of the abdomen or contrast enhanced magnetic resonance imaging.
Detection of tumor thrombi has previously demonstrated as possible during cardiac ultrasound examination. This case, to the best of our knowledge is the first demonstration of IVC filter thrombus detected during ultrasound imaging of the inferior vena cava.

As IVC ultrasound becomes further accepted in daily clinical practice there will be increased incidence of associated findings. Thus it is important to recognize the ultrasonographic appearance of IVC thrombosis, as quick recognition of this finding may shorten time to diagnosis. Acceptance of this finding as diagnostic may additionally save patients from the increased risk of intravenous contrast during CT or MRI angiography.

We have described a case where bedside ultrasound changed management in a very significant way. Bedside ultrasound allowed identification of the pathology early in the clinical course, guided additional imaging and lead to surgical procedure and re-initiation of anticoagulation. Without early bedside ultrasound, given the patients presentation of anemia and menorrhagia, these interventions especially the surgery and anticoagulation would not have taken place.

Conclusion
Use of IVC ultrasound may detect superiorly extending IVC filter thrombosis.