Study purpose: This study will investigate anatomical factors associated with increased risk of major adverse aorta-related event and accelerated growth of abdominal aneurysm based on 3-dimensional analysis of CT images.

Study design: a multicenter single-arm prospective observational study.

Subject: patients with small abdominal aortic aneurysm with maximal diameter of 30-50 mm (n=323)

Methods: Patients diagnosed with small AAA based on CT will be enrolled after considering inclusion and exclusion criteria and prospectively followed clinically and with CT at 1 year.

Primary endpoint: Major adverse aorta-related events (death, aortic rupture, or aneurysm growth >0.4 cm per year) at 1 year

Secondary endpoints: 1) clinical events : death, aortic rupture, aneurysm growth >0.4 cm per year, surgical or endovascular repair 2) Changes in CT parameters of aneurysm: diameter, volume, wall shear stress

Prospective single-arm multicenter registry

Inclusion Criteria:

- abdominal aortic aneurysm with maximum diameter of 30-50 mm

Exclusion Criteria:

• Age <19 years
• Serum Cr> 1.5mg/dL or eGFR<30 mL/min
• Known allergic reactions to iodine contrast media
• Women in pregnancy or women of childbearing age
• Abdominal aortic aneurysms indicated for endovascular or surgical repair (symptomatic aneurysm or aneurysms with diameter >5cm)
• Saccular type aneurysm, infected or inflammatory aneurysm
• Combined aortic dissection
• Aneurysms associated with genetic or connective tissue diseases (Marfan syndrome, Shprintzen-Goldberg syndrome, Loeys-Dietz syndrome, Takayasu's arteritis, Behcet's disease)
• Past history of surgical or endovascular repair of aorta
• Any surgical or endovascular repair planned within 1 year
• Life expectancy < 1 year

patients with small abdominal aortic aneurysm with maximal aneurysm of 30 ~50 mm