Background: An aortic aneurysm is defined as a 50% or greater increase in diameter compared with normal levels or the level of the left renal vein. However, normal diameters for many aortic segments are not known, and the aortic segment at the left renal vein may be enlarged. The purpose of this study was to determine normal diameters of the thoracic and abdominal aortas in relationship to age, gender, and body size.
Methods: Aortic diameters (ADs) were determined at four anatomic levels: thoracic aorta, abdominal aorta at the celiac axis, renal arteries, and midway between the renal arteries and the bifurcation. ADs were determined with the use of a video analyzer and an electronic caliper. Computed tomographic scans (n = 389) obtained for nonvascular diagnoses were analyzed according to gender, age, height, weight, and body surface area (BSA).
Results: At all levels and in each decade the AD is significantly greater in men than in women (p < 0.0001). BSA is a better predictor of size than height or weight. AD increased with age at all levels, and there was a positive correlation between the AD and BSA and gender. Expected ADs for each aortic segment may be calculated according to regression equations. Age-, gender-, and BSA-matched patients with abdominal aortic aneurysms revealed significant enlargements in all proximal aortic segments.
Conclusions: AD at a given level is a function of gender, age, and BSA. When these variables are known, it is possible to calculate an expected AD. The AD is greater at all levels in patients with abdominal aortic aneurysms and in men compared with women.