Growth rates of small abdominal aortic aneurysms assessed by computerised tomography--a systematic literature review

Most current evidence examining abdominal aortic aneurysm (AAA) growth is based on ultrasound surveillance.

This review aimed to systematically analyse studies which have assessed small AAA growth using computed tomography (CT) to monitor outcome.

Studies investigating small AAA expansion rates using CT images were identified by searching the PubMed database and hand searching article reference lists. Eligible studies must have focused on monitoring small AAA growth using CT and included patients with baseline AAA diameters <55 mm for which growth rates were reported.

Ten studies including 845 patients met eligibility with average baseline AAA diameters ranging from 36.2 to 50.5 mm. AAA growth was assessed using axial (n = 1), orthogonal (n = 2), anterior to posterior (n = 4), and unspecified (n = 3) measurement methods. One study reported the reproducibility of their assessment method. Mean AAA diameter growth rates ranged from 2.6 to 5.2 mm/year. Factors reported to be associated with increased AAA expansion included: large AAA thrombus size (n = 3 studies), large baseline AAA diameter (n = 2), high AAA wall stress, elevated plasma concentration of matrix metalloproteinase-9 and presence of carotid artery disease (n = 1 study each). Factors reported to be negatively associated with AAA growth included presence of diabetes mellitus and chronic limb ischaemia (n = 1 study each).

Many currently reported studies assessing small AAA growth on CT fail to report consistent use of reproducible measurement methods. CT offers the opportunity to assess orthogonal diameter and perform central reading which could be an advantage of this form of imaging.