Ultrasound of the radial aspect of the wrist was performed. On examination there was an erythematous mass overlying the distal radius on the volar aspect of the wrist.
Ultrasound demonstrated that this mass was a radial artery aneurysm measuring 14 mm in length with a diameter of 6 mm (normal size 2 mm). The aneurysm had a broad neck and was partially thrombosed. Doppler signal showed the classic "yin and yang" flow. Thrombus is seen extending proximally up the radial artery.