I saw the sign: He felt a pang and we saw the Yin-Yang (sign).

The yin-yang sign, also known as the Pepsi sign, is used to describe the classic appearance of bidirectional blood flow within an aneurysm or pseudoaneurysm sac on color Doppler ultrasound. The corresponding spectral Doppler finding is a "to-and-fro" waveform, caused by inflow to the aneurysm/pseudoaneurysm sac during systole and outflow during diastole. It is important to recognize this sign in order to quickly identify the presence of an aneurysm or pseudoaneurysm and prevent complications such as expansion and rupture.