In a patient with a suspected abdominal aortic aneurysm, which is the best initial diagnostic study?

In a patient suspected of having an abdominal aortic aneurysm (AAA), ultrasound (US) is recognized as the best initial diagnostic study. This is largely due to its non-invasive nature, availability, and effectiveness in quickly assessing the presence of an AAA. Ultrasound can provide clear images of the aorta and can accurately measure its diameter, which is pivotal in determining whether an aneurysm is present and whether intervention is necessary.

The use of ultrasound is particularly advantageous because it does not expose patients to ionizing radiation and can be performed at the bedside, making it accessible in various clinical settings. Moreover, it has a high sensitivity and specificity for diagnosing AAA, especially in patients with abdominal symptoms.

In contrast, while other imaging modalities such as magnetic resonance imaging (MRI) or arteriography can be used for further evaluation of the aneurysm or to assess complications, they are not typically the initial study of choice. Similarly, plain film imaging has limited utility in diagnosing AAA as it lacks the detailed visualization of the aorta needed to reliably confirm the diagnosis. Therefore, ultrasound stands out as the most appropriate first step in the diagnostic process for suspected abdominal aortic aneurysm.