Background: Chronic inflammation is a hallmark characteristic in the patho-physiology of abdominal aortic aneurysms (AAA) and atherosclerosis. These two conditions also share a number of risk factors; however it is thought that their pathophysiologies are different. In this study we sought to prospectively investigate whether there was a greater degree of inflammation in the aortas of AAA patients compared to matched controls with atherosclerosis.

Methods: The aortas of 20 patients with infra-renal AAA and 20 age, sex and risk factor-matched controls with atherosclerotic disease were imaged using fluoro-deoxyglucose positron emission tomography (FDG-PET) with CT co-registration. Uptake of tracer directly reflects metabolic activity and has been shown to correlate with macrophage activity. Tracer uptake was analysed in various arterial segments by measuring maximum standard uptake values (SUV). Inflammatory biomarkers, including hsCRP, were also measured.

Results: The mean aneurysm diameter was 44mm (SD+/−9mm). Patients with AAA had higher uptake of FDG in the abdominal aorta compared with controls (SUV 2.19 vs. 1.99, p=0.02). The greatest uptake was seen in the aneurysmal sac (mean SUV 2.28 +/−0.55). AAA patients also had a higher level of serum inflammatory markers (hsCRP 2.76 vs. 1.74mg/L, p=0.03).

Conclusions: This study demonstrates there is greater in-vivo metabolic activity in patients with AAA. This suggests there is higher inflammatory cell load within the aortic wall in patients with AAA as reflected by higher levels of FDG uptake. This highlights the importance of targeting inflammation as a therapeutic strategy.