The yin-yang sign indicates bidirectional flow due to swirling of blood within the (true or false) aneurysm.
The patent portion of the lumen of the aneurysmal vessel demonstrates increased attenuation, due to contrast enhancement, whereas a part of the lumen shows reduced attenuation due to mural thrombus.
History and etymology
It is named after the symbol representing the Chinese philosophers' thoughts to describe how opposing forces are interconnected and interdependent. It has also been likened to the logo for Pepsi, the well-known cola beverage.
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