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Chest Imaging

E2563. Uncommon Filling Defects: Nonthrombotic Pulmonary Embolism on CT

Jon A,  Maldjian P. Rutgers Biomedical Health Science University Hospital, Newark, NJ

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Background Information: The pulmonary arterial bed functions as a first-pass capillary network trapping various substances introduced into the systemic venous circulation. Although pulmonary thromboembolism is the most common disorder producing filling defects in the pulmonary vasculature on CT, radiologists should also be familiar with the appearance of other entities that can embolize to the right heart and pulmonary vessels. Nonthrombotic pulmonary embolism is defined as embolization to the pulmonary vasculature of gas, bacteria, cells, foreign substances, and foreign bodies. The purpose of this presentation is to illustrate and discuss the CT appearance of various types of nonthrombotic embolism to the pulmonary circulation.

Educational Goals/Teaching Points: The goals of this exhibit are to illustrate and describe the appearances on CT of various causes of nonthrombotic embolism to the pulmonary circulation. The relevant pathophysiology, clinical manifestations, and treatment of these disorders are also discussed.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: We organize the CT appearances of nonthrombotic pulmonary embolism into three categories: low attenuation filling defects, catheter fragments, and high attenuation or metallic foreign bodies. For low attenuation abnormalities, we discuss air embolism, septic emboli, tumor emboli, and hydatid embolism. For catheter embolization, we show examples of fragments from different types of catheters. For high attenuation and metallic attenuation foci in the pulmonary circulation, we include depictions of embolization from prostate radiotherapy seeds, bullets, needle fragments, iodinated oil and polymethylmethacrylate. In this exhibit, we also demonstrate how scrutinizing additional radiologic findings within and outside of the thoracic cavity can help to clarify the underlying embolic agent.

Conclusion: Nonthrombotic emboli to the pulmonary circulation are an uncommon cause of filling defects on CT imaging of the pulmonary vasculature. These emboli have diverse etiologies and appearances. Familiarity with the specific imaging features of various embolic agents and scrutiny of thoracic and extrathoracic radiologic findings should facilitate accurate identification of nonthrombotic causes to determine appropriate therapy.