From the Guidelines
The normal dimension of the infrarenal abdominal aorta is up to 2 cm in the anteroposterior (AP) diameter. When considering the size of the aorta, it's essential to take into account the specific segment being measured, as well as individual factors such as age, gender, and body size. In the context of diagnosing and managing abdominal aortic aneurysms (AAAs), understanding the normal aortic dimensions is crucial, as aneurysms are defined as a localized arterial dilatation ≥50% of the normal diameter 1. The term ectasia is applied to arterial dilatations <50% of the expected normal diameter, and the infrarenal abdominal aorta is considered aneurysmal if it is ≥3 cm in diameter or ectatic if it is between 2 and 3 cm in diameter 1. Key points to consider when evaluating aortic size include:
- The absolute threshold for aneurysm decreases along the length of the aorta and is about 10% smaller in women than in men 1.
- Imaging studies, such as ultrasound or CT scans, are important in determining the size and extent of an AAA, as well as any associated significant stenosis or aneurysm involving abdominal visceral and extremity arteries 1.
- Elective repair is considered for AAAs ≥5.5 cm in diameter, while smaller AAAs require periodic surveillance at intervals based on their maximum size 1. Overall, accurate measurement and interpretation of aortic size are critical in preventing morbidity and mortality associated with aortic aneurysms.
From the Research
Normal Aorta Size
The normal size of the aorta can vary depending on factors such as age, gender, and body surface area.
- According to a study published in the Journal of Magnetic Resonance Imaging 2, the upper limits of body surface area indexed ascending aortic luminal diameter for age categories of 45-54,55-64,65-74, and 75-84 years are 21,22, and 28 mm/m(2) in women and 20,21,22,23 mm/m(2) in men, respectively.
- Another study published in Radiology 3 established effective aorta diameter standards at multiple levels of the thoracic aorta, abdominal aorta, and common iliac arteries in healthy children, which can be used to calculate z scores.
Factors Affecting Aorta Size
Several factors can affect the size of the aorta, including:
- Age: The aorta diameter increases gradually with aging for both genders among all race/ethnicities 2.
- Gender: Men tend to have a larger aorta diameter than women 2.
- Body surface area: The aorta diameter is also related to body surface area, with larger individuals tend to have a larger aorta diameter 2.
- Hypertension: Hypertensive subjects tend to have a larger aorta diameter than normotensives 2.
Abnormal Aorta Size
An abnormal aorta size can be an indication of underlying conditions such as aneurysms or hypoplasia.
- A study published in Clinical Cardiology 4 found that patients with bicuspid aortic valve disease who had a maximal aortic diameter of 4.5 cm or greater had lower odds of being on preoperative statins compared to those with a maximal aortic diameter less than 4.5 cm.
- Another study published in Experimental and Clinical Cardiology 5 discussed the risk factors for abdominal aortic aneurysms, including age, smoking, hypertension, and Caucasian ethnicity.