Ultrasound Case 055


A 78 year old woman has a pulsatile mass in her mid abdomen. You wonder whether it is an abdominal aortic aneurysm.

Describe and interpret these scans

Image 1: Transverse view abdominal aorta with colour Doppler. There is a 65mm abdominal aortic aneurysm.

LITFL Top 100 Ultrasound 055 03 Ying and Yang sign
Yin and Yang sign


Abdominal aortic aneurysm (AAA)

Blood flowing through a dilated artery often spirals as it swirls through the dilated passage.

Colour Doppler interrogation shows the flow rushing towards the probe up one wall (red) and then swirling away down the other wall (blue). This can create a Yin and Yang appearance.

The Yin and Yang sign is most typical with flow through a pseudoaneurysm but can also be seen in other aneurysms.



An Emergency physician based in Perth, Western Australia. Professionally my passion lies in integrating advanced diagnostic and procedural ultrasound into clinical assessment and management of the undifferentiated patient. Sharing hard fought knowledge with innovative educational techniques to ensure knowledge translation and dissemination is my goal. Family, wild coastlines, native forests, and tinkering in the shed fills the rest of my contented time. | SonoCPDUltrasound library | Top 100 | @thesonocave |

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