Abdominal aortic aneurysm overview

Abdominal Aortic Aneurysm Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Abdominal aortic aneurysm, also written as AAA and often pronounced 'triple-A', is a localized dilatation of the abdominal aorta, that exceeds the normal diameter of the abdominal aorta by more than 50%.

Historical Perspective

The etymology of the word aneurysm comes from the Greek word for "dilatation". Abdominal aortic aneurysm as a medical condition has been recognized since ancient times, but was not been successfully treated until the early part of the 20th century.

Definition

The normal diameter of one's aorta depends on the patient's age, sex, height, weight, race, body surface area, and baseline blood pressure. On average, the normal diameter of the infrarenal aorta (where abdominal aortic aneurysms are located) is 2 cm. Therefore an abdominal aortic aneurysm is defined as a dilation of 3.0 cm or more.

An abdominal aortic aneurysm is to be distinguished from aortic ectasia which is defined as a mild generalized dilatation (<50% of the normal diameter of ≤ 2.9 cm) that is due to age-related degenerative changes in vessel wall.

Anatomy

A plate from Gray's Anatomy with yellow lines depicting the most common infrarenal location of the AAA.

The aorta below the renal arteries, also known as the infrarenal aorta, is the location of 90% of abdominal aortic aneurysms. Other possible locations are suprarenal and pararenal. The aneurysm can extend to include one or both of the iliac arteries.

Classification

Aneurysms are usually classified by their shape:

Fusiform Aneurysms

• Most common type seen in the infrarenal aorta
• Diffuse, circumferential

Saccular Aneurysms

• Involve only a portion of the circumference, with a characteristic outpouching of the vessel wall.

Pathophysiology

The underlying pathophysiology of abdominal aortic aneurysm involves genetic influences, smoking, hypertension, hemodynamic influences and underlying atherosclerosis. In rare instances infection, arteritis, and connective tissue disorders may play a role.

Differentiating Abdominal Aortic Aneurysm from other Disorders

An abdominal aortic aneurysm should be differentiated from other causes of abdominal pain such as acute cholecystitis.

Videos on Abdominal Aortic Aneurysm

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Acknowledgements

The content on this page was first contributed by: C. Michael Gibson M.S., M.D. Template:WH Template:WS