Injecting Point of care Ultrasound into your practice: A case of a femoral artery pseudoaneurysm in the Emergency department

Abstract Background Patients with a history of intravenous drug use (IVDU) frequently present to the emergency department (ED) with extremity pain and swelling. While soft tissue infections are the most common injection-related complications, pseudoaneurysms are a serious vascular complication that can mimic soft tissue infections on physical examination. Misdiagnosis of a pseudoaneurysm as an abscess may lead to inappropriate incision and drainage, resulting in life-threatening hemorrhage. Point-of-care ultrasound (POCUS) is a rapid bedside tool that can reliably differentiate these entities. Case Presentation: A 36-year-old male with a history of antiphospholipid syndrome and pulmonary embolism, on warfarin, presented with two weeks of progressive right thigh pain and swelling. He endorsed injecting intravenous drugs into the affected area. Examination revealed erythema, induration, and a palpable mass. Laboratory studies were notable for a supratherapeutic international normalized ratio (INR) of 8.9. POCUS was performed as the initial imaging study, demonstrating a large hypoechoic structure with bidirectional "to-and-fro" flow on color Doppler—the "yin-yang sign"—consistent with a femoral artery pseudoaneurysm. Computed tomography angiography (CTA) confirmed an 8.6 × 6.6 × 12.1 cm pseudoaneurysm with active hemorrhage at the common femoral artery bifurcation. The patient received empiric broad-spectrum antibiotics and underwent right external iliac to superficial femoral artery bypass with bovine carotid graft. He was discharged home on hospital day eight. Conclusions This case demonstrates the value of bedside POCUS as a first-line imaging tool for differentiating pseudoaneurysms from soft tissue infections in patients with IVDU. Emergency physicians should maintain a low threshold for performing POCUS with color Doppler in this population, particularly in the setting of concomitant anticoagulation.