Clinical introduction A 45-year-old man with no past medical history presents with bilateral lower extremity pain and perineal numbness after walking 10–15 min. The pain starts in his bilateral buttocks and radiates down into his thigh and into his toes. He has no back pain, fever, difficulty urinating or stooling, incontinence or trauma. Social history is positive for smoking. Physical examination was only remarkable for non-dopplerable lower extremity pulses, and he was unable to ambulate down the ED hallway without becoming symptomatic. Ultrasound of his abdominal aorta (figure 1) was performed.

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Figure 1

Transverse view of distal abdominal aorta, just proximal to the bifurcation. (A) The aorta without Doppler. (B) The same image with Doppler mode activated.

Question What is the most likely diagnosis based on the image?

A. Lumbar stenosis

B. Abdominal aortic aneurysm

C. Aortic thrombus

D. Aortic dissection