MSCT Assessment of Perivascular Adipose Tissue and Visceral Fat Characteristics in Aortic, Iliac, and Lower Limb Aneurysms

Background: Perivascular adipose tissue (PVAT) plays a significant role in the atherosclerotic processes of arteries and aneurysmal occurrence and can be assessed by increased PVAT density in Hounsfield units (HU) on MSCT. Our objectives were to examine possible differences and associations of PVATs in several locations of aneurysmal occurrence (abdominal aorta, iliac, and lower extremity arteries), measured on the aneurysmal site and the same location on an unaffected artery. Also, we examined the possible association of aneurysmal PVAT with visceral fat parameters. Methods: In this retrospective and cross-sectional study, a total of 198 patients were included and divided into four groups: single abdominal aortic aneurysm (AAA, n = 55), single iliac artery aneurysm (n = 36), single lower extremity (leg) artery aneurysms of femoral or popliteal arteries (n = 43), and multiple aneurysms in one individual (AAA and iliac artery, n = 64). PVAT density measurements were performed at the level of the widest lumen of the aneurysm and at the same level on the contralateral artery. Aneurysmal diameter and thrombus width were also measured. The volume and the mean attenuation of visceral fat were automatically calculated by manually designating the targeted segmentation anatomical item. Results: A difference in PVAT densities among the first three groups of patients with a single aneurysm at different location was found (p = 0.027), as well as at the contralateral side (p < 0.001). In patients with multiple aneurysms, higher PVAT density was found at the iliac site compared to the AAA site (p = 0.002, paired test). Aneurysm diameter correlated to thrombus width, but not with PVAT densities. Comparison of PVAT densities with visceral fat densities showed moderate positive correlation (r = 0.446, Pearson correlation coefficient; ρ = 0.387, Spearman rank correlation; p ≤ 0.001), that was significant in the case of abdominal and iliac artery aneurysms, but not with leg aneurysms. Conclusions: Increased densities of PVAT were found on the aneurysmal site, suggesting its probable role in aneurysmal occurrence. PVAT density varied according to aneurysm location. Visceral fat may be associated with increased PVAT density and aneurysm development in abdominal and iliac regions, whereas this association was not observed in leg aneurysms.