Computed tomography attenuation of periaortic adipose tissue in abdominal aortic aneurysms

Purpose: To assess periaortic adipose tissue attenuation on CT angiography in
different abdominal aortic aneurysm disease states.
Materials and Methods: In a retrospective observational study from January 2018 to December 2022, periaortic adipose tissue attenuation was assessed on CT
angiography in patients with asymptomatic or symptomatic (including rupture)
abdominal aortic aneurysms, and control individuals without aneurysms. Adipose
tissue attenuation was measured using semi-automated software in periaortic
aneurysmal and non-aneurysmal segments of the abdominal aorta, and in
subcutaneous and visceral adipose tissue. Periaortic adipose tissue attenuation
values between the three groups was assessed using Students t-test and Wilcoxon rank sum test followed by a multi-regression model.
Results: Eighty-eight individuals (median age, 70 [IQR, 65-78] years; 78 male and 10 female) were included: 70 patients with abdominal aortic aneurysms (40 asymptomatic and 30 symptomatic including 24 with rupture), and 18 controls. There was no evidence of differences in the periaortic adipose tissue attenuation in the aneurysmal segment in asymptomatic patients versus controls ((-81.44±7 versus -83.27±9 HU, Hounsfield units, P=0.43) and attenuation in non-aneurysmal segments between asymptomatic patients versus controls (-75.43±8 versus -78.81±6 HU, P=0.08).
However, symptomatic patients demonstrated higher periaortic adipose tissue
attenuation in both aneurysmal (-57.85±7 HU, P<0.0001) and non-aneurysmal
segments (-58.16±8 HU, P<0.0001) when compared with the other two groups.
Conclusions: Periaortic adipose tissue CT attenuation was not increased in stable
abdominal aortic aneurysm disease. There was a generalised increase in attenuation in patients with symptomatic disease, likely reflecting the systemic consequences of acute rupture.