Which description best defines a saccular aneurysm?

• A. Fusiform
• B. Abrupt dilation with sharply defined neck
• C. Uniform dilation along the vessel
• D. No dilation, just wall thickening

Answer: (B)

A saccular aneurysm is a focal, pouch-like outpouching from the artery that has a distinct, narrow neck connecting it to the parent vessel. This sac-like projection on one side distinguishes it from a fusiform dilation, which runs around the entire circumference as a uniform dilation along a segment. So the abrupt dilation with a sharply defined neck best describes a saccular aneurysm, whereas uniform dilation describes a fusiform aneurysm, and wall thickening without dilation does not represent an aneurysm.