How does a true aneurysm differ from a false aneurysm?

A true aneurysm is characterized by the dilation of an artery that involves all three layers of the arterial wall: the intima, media, and adventitia. This forms a true "pouch" that maintains the integrity of the original vessel wall structure, allowing the aneurysm to be classified as an expansion of the vessel rather than a breach or injury.

In contrast, a false aneurysm, or pseudoaneurysm, occurs when there is a disruption of the arterial wall, leading to a contained rupture where blood escapes into the surrounding tissue but is still contained by a fibrous capsule. Therefore, false aneurysms do not involve all three layers of the arterial wall.

Recognizing the distinction between these two types of aneurysms is crucial for understanding their potential complications, management, and treatment, as true aneurysms are more likely to be asymptomatic and discovered incidentally, while false aneurysms might present with more acute symptoms due to their nature of involving extravascular structures.