Definition: Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Input: Abstract: Recurrent pulmonary embolism from the lower extremities or pelvis, despite anticoagulation, often requires interruption of the inferior vena cava (IVC). We report two patients in whom interruption of the IVC failed to ameliorate symptoms. Both patients demonstrated a previously unrecognized duplication of the IVC. We stress the importance of excluding abdominal venous anomalies prior to interrupting the IVC using surgical or percutaneous methods.

Human