Objectives: To determine predictors related to abdominal aortic aneurysm (AAA) development following a "normal" aortic ultrasound scan.
Design, materials & methods: Over a 23-year period, 22 961 men participated in an AAA screening programme. Maximum aortic diameter of less than 30 mm was deemed "normal". 4308 of these "normal" individuals were later re-scanned at intervals for research purposes.
Results: AAA prevalence was 4.4% at initial scanning. In those with a normal scan, 46 patients subsequently presented with AAAs incidentally detected and 120 (2.8%) had AAAs identified as part of the ongoing surveillance. The median initial aortic size of these 166 men was 25 mm (range 15-29 mm). Over the follow-up period, there have been 24 (14%) AAA-related deaths, 24 patients underwent successful AAA surgery and 36 died of unrelated causes. In those with an initial aortic diameter of <25 mm who later developed an AAA, the odds ratio for AAA-related mortality was 2 (95% CI 1-4.1, p=0.03, x(2)).
Conclusion: AAAs can develop following an initial "normal" scan and men with an aortic diameters of 25-29 mm appear to be at greater risk. Surveillance for this sub-group may further reduce the incidence of undiagnosed AAA and AAA-related mortality.