This was diagnosed by CT scan after being found on x-ray. An aneurysm is a dilation of a blood vessel.
Smoking also contributes significantly.
The areas where they can be dangerous are in the aorta. The risk is of an aneurysm is rupture resulting in sudden death. This risk increases as the size of the aneurysm increases. In general when the aneurysm is 4-6 cm an operation is indicated to repair the aneurysm. This is major surgery but is usually well tolerated.