A patient presents with a painful, pulsatile groin mass foll…
A patient presents with a painful, pulsatile groin mass following a recent cardiac catheterization. Color Doppler of the mass reveals a swirling “Yin-Yang” color flow pattern within a fluid collection adjacent to the common femoral artery, and spectral Doppler of the connecting neck demonstrates a classic “to-and-fro” waveform. What is the likely diagnosis?