What is an aneurysm
As a result of atherosclerosis the artery wall becomes weakened and balloons out. The most common artery to be affected is the aorta. This is the main artery that comes from the heart and carries blood to the rest of the body. The most common part of the aorta that is affected is below the point where the arteries to the kidneys (renal arteries) come off:
The aneurysm can extend above the renal arteries (suprarenal aneurysm) and into the chest (thoracic aneurysm). These are more serious conditions with more risks during surgery.
In addition to the aorta, other common sites of aneurysm formation are the iliac arteries (continuation of the aorta), the femoral arteries (groins) and the popliteal arteries (behind the knees).
The figure below shows how aneurysms are classified:
A false aneurysm refers to the situation where blood leaks out of a small hole in the artery and forms a 'haematoma' (collection of blood). This becomes encased in scar tissue and can continue to grow. They arise after angiogram, angioplasty, trauma or at the join between a graft and the artery.
True aneurysm means that the artery wall is intact and this can balloon out symmetrically for form a 'fusiform' aneurysm or there can be a local 'blow-out' to form a 'saccular' aneurysm. As these aneurysms grow there is a risk of rupture.
A 'dissecting' aneurysm is an uncommon event. It happens when the blood stream forces its way into the artery wall and causes it to stretch. These aneurysms can cause problems by rupturing or blocking off the normal channel in the artery.