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An aneurysm is a localised balloon-like dilatation of a blood vessel. It is caused by a weakening of the vessel wall or may be secondary to infection or disease such as arteriosclerosis.

True Aneurysm

A true aneurysm occurs when the inner layers bulge through the outer layer that contains them. Therefore, an aneurysm is surrounded by these inner layers.

An abdominal aortic aneurysm (AAA) (Figure 1) is a common example of a true aneurysm.

False Aneurysm

A false or pseudo-aneurysm is a collection of blood which leaks out of an artery or vein and is held in close contact with the vessel by the surrounding tissue.

The blood may clot, but the aneurysm may rupture leading to tracking of blood through layers of soft tissue.

False aneurysms can be produced by trauma involving puncture of an artery.

Iatrogenic causes can occur such as following the percutaneous puncture of an artery when performing arteriography (Figure 2).

An increasing problem is the development of false aneurysms in drug addicts who have exhausted most of the venous routes used for the injection of their addictive drugs.

Often the needle is not sterile having been used before by perhaps several addicts adding to localised sepsis which can exacerbate the problem.