What type of aneurysm is indicated if a sonogram shows an elliptical expansion of the vessel wall?

In the context of sonography findings, an elliptical expansion of the vessel wall is characteristic of a dissecting aneurysm. This type of aneurysm occurs when there is a tear in the intima (the innermost layer) of the blood vessel wall, allowing blood to flow between the layers of the vessel wall, creating a false lumen. The shape appears elliptical due to the nature of how the blood separates the layers of the vessel wall.

A true aortic aneurysm, in contrast, typically involves an outward bulging of all three layers of the vessel wall, resulting in a more rounded or saccular appearance on imaging. A mycotic aneurysm is an infection-induced aneurysm and might have different characteristics depending on its location and the underlying infection. A pseudoaneurysm, which involves a hematoma that communicates with the vessel lumen, usually produces a different echogenic pattern on ultrasound and does not typically present as an elliptical expansion of the wall but rather as an irregular collection of blood.

In summary, the elliptical appearance of the vessel wall specifically points to the characteristics of a dissecting aneurysm, where the layers of the vessel wall are compromised, leading to this unique sonar signature.