Management of Small Infrarenal Abdominal Aortic Aneurysms

Definition and Classification

The American College of Radiology defines an infrarenal abdominal aortic aneurysm (AAA) as a localized dilatation of the abdominal aorta below the renal arteries with a diameter ≥3 cm, representing at least a 50% increase from the normal aortic diameter 2
The normal dimension of the infrarenal abdominal aorta is up to 2 cm in anteroposterior diameter, according to the American College of Radiology 1
An AAA with a diameter of 3.1 cm is just above the threshold for classification as an aneurysm, as stated by the American College of Radiology 1

For AAAs measuring 3.0 to 3.4 cm in diameter, the American College of Radiology recommends surveillance imaging every 3 years 1, 2
The American College of Radiology recommends ultrasound as the first-line imaging modality for surveillance of AAAs due to its non-invasive nature, lack of radiation exposure, and cost-effectiveness 3, 2
The American College of Radiology suggests considering CT angiography or MR angiography if ultrasound visualization is inadequate due to body habitus or bowel gas 3

The American College of Cardiology advises patients with AAAs to stop smoking and offers smoking cessation interventions, as smoking is strongly associated with AAA development and expansion 4
The American College of Cardiology recommends monitoring and controlling risk factors, including hypercholesterolemia 2 and family history of AAA 3
The American College of Cardiology suggests considering beta-adrenergic blocking agents to reduce the rate of aneurysm expansion 4, 5

The American College of Cardiology states that at 3.1 cm, intervention is not recommended as the risk of rupture is low 4, 6
The American College of Cardiology recommends intervention when the AAA diameter reaches ≥5.5 cm in men or ≥4.5-5.0 cm in women 4 or when the aneurysm becomes symptomatic regardless of size 4, 6
The American College of Cardiology also recommends intervention when rapid expansion occurs (>0.5 cm in 6 months) 2

The American College of Cardiology recommends that men 60 years of age or older who are siblings or offspring of patients with AAAs undergo ultrasound screening 4, 5

The American College of Radiology notes that AAAs are typically asymptomatic until rupture, which carries a mortality rate of 75-90% 3
The American College of Cardiology states that the risk of rupture increases with aneurysm size, female gender, smoking, and hypertension 2
The American College of Radiology advises avoiding missed scheduled surveillance imaging as AAAs can expand unpredictably 1