Ultrasonic visualization of the posterior thoracic aorta in long axis: diagnosis of a saccular mycotic aneurysm.

A saccular aneurysm arising from the descending thoracic aorta was identified ultrasonically in a 60-year-old man with a subsequent pathologic diagnosis of a Listeria monocytogenes mycotic aneurysm. A cross-sectional scanning technique, which permitted visualization of the descending thoracic aorta in long axis, demonstrated a 3 X 5 cm relatively echo-free mass between the heart and the aorta. A communication between the mass and the aorta established the diagnosis of an aneurysm.