Aortic Size and Height Indices in Abdominal Aortic Aneurysms

The goal of this observational study is to learn whether adjusting abdominal aortic aneurysm (AAA) size for body size helps distinguish ruptured from intact aneurysms better than maximum aneurysm diameter alone. The study will evaluate the Aortic Size Index, which adjusts aneurysm diameter for body surface area, and the Aortic Height Index, which adjusts aneurysm diameter for height. The main questions are: 1. Do the Aortic Size Index or Aortic Height Index distinguish ruptured from intact AAAs better than maximum aneurysm diameter alone? 2. What proportion of ruptured AAAs occur below the diameter thresholds of 55 millimeters for men and 50 millimeters for women? 3. Do the findings vary according to sex, participating country, or participating center? The study will include adults presenting with a ruptured infrarenal AAA and adults with an intact infrarenal AAA undergoing open surgical or endovascular repair. Participants will not receive an experimental treatment. Researchers will use computed tomography scans obtained before surgical or endovascular treatment and available height and weight measurements. No additional computed tomography scans will be required for the study. Researchers will also collect clinical, operative, and mortality information. Vital status will be recorded during the repair procedure, during the index hospitalization, and at 30-day follow-up. For participants who undergo AAA repair, the 30-day period will begin on the date of repair. For participants who do not undergo repair, it will begin on the date of the index clinical presentation. The 30-day assessment will use institutional medical records or telephone contact when necessary.

Inclusion Criteria: * Age 18 years or older. * Documented ruptured infrarenal abdominal aortic aneurysm (AAA) with adequate computed tomography (CT) imaging obtained before any surgical or endovascular intervention, regardless of whether repair is subsequently performed; or intact infrarenal AAA undergoing open surgical or endovascular repair. * Availability of CT imaging of sufficient quality for standardized measurement of maximum aneurysm diameter. * Availability of height and weight data obtained and documented according to the prespecified anthropometric measurement hierarchy, including the source and date of each measurement. * Written informed consent from the participant or a legally authorized representative when required and feasible, according to the ethics-approved procedures applicable at each participating center. Exclusion Criteria: * Age younger than 18 years. * Aneurysm not classified as infrarenal. * Absence of adequate CT imaging obtained before any surgical or endovascular intervention, or imaging of insufficient quality to reliably measure maximum aneurysm diameter. * Absence of any usable height or weight value from the prespecified anthropometric measurement hierarchy, precluding calculation of the Aortic Size Index (ASI) and Aortic Height Index (AHI). * Active pregnancy at the time of enrollment. * Refusal to participate or withdrawal of informed consent.