How to define an abdominal aortic aneurysm--influence on epidemiology and clinical practice.

Abdominal aortic aneurysm (AAA) is a dilatation of the abdominal aorta. There is, however, no general agreement on how to define an AAA. The lack of a uniform definition may have consequences on epidemiology and clinical practice. Several proposed definitions of an AAA exist, all based on the diameter of the abdominal aorta. Age, gender, and body size are all associated with the aortic diameter, and may therefore also be of importance when evaluating the aortic diameter. The precision of the measurement and the awareness of imaging shortcomings are also important. In order to demonstrate a true widening of the aorta the relation to adjacent aortic segments must be assessed. To demonstrate an expansion of a potential aneurysm, a follow-up period with repeated assessments is required. Thus, a fixed diameter does not serve as a proper definition of an aneurysm, but rather as a cut-off level for further assessment and/or follow-up.