American Board of Internal Medicine (ABIM) Certification Practice Exam

At what anteroposterior diameter is an abdominal aortic aneurysm considered present?

1. 2.5 cm

2. 3.0 cm

3. 4.0 cm

4. 5.0 cm

The correct answer is: 3.0 cm

An abdominal aortic aneurysm (AAA) is typically defined as a localized dilation of the abdominal aorta that exceeds the normal diameter. Normal aortic diameter in adults ranges from 2.0 to 3.0 cm, and it is when the diameter exceeds 3.0 cm that it is generally considered an aneurysm. While a diameter of 4.0 cm is commonly referenced as a threshold for surgical intervention or increased monitoring due to the increased risk of rupture, the classification of the presence of an AAA begins at 3.0 cm. Therefore, the rationale for the correct answer hinges on the understanding that once the abdominal aorta's diameter reaches 3.0 cm, it is classified as an aneurysm by the standards of vascular imaging. This classification is critical for determining appropriate management strategies, as the risks associated with larger aneurysms necessitate closer monitoring or surgical intervention. Thus, identifying the threshold at which an abdominal aortic aneurysm is considered present is essential for effective clinical practice and patient management.