The incidence of small abdominal aortic aneurysms and the change in normal infrarenal aortic diameter: implications for screening.
OBJECTIVE
to study the incidence of small abdominal aortic aneurysms (AAA), and to investigate what proportion of normal infrarenal aortic diameters (IAD) expand with age.


METHODS
longitudinal follow-up in a population-based aneurysm screening programme. The infrarenal aortic diameter (IAD) was measured by ultrasound. A second scan was performed in subjects with a normal aorta after an average of 5.5 years.


RESULTS
data were analysed from 4072 subjects, 464 with a small AAA and 3608 with a normal aorta. The infrarenal aorta expanded in 15% of subjects, but significant growth (>5 mm) occurred in only 7%. Age and initial diameter were independent predictors for aortic dilatation. The effect of diameter at first screen was non-linear. The relative risk for expansion increased dramatically for IADs over 2.5 cm (test for departure of trend: chi2=52, p<0.0001). The effect of age was also non-linear, the risk of expansion was highest in the 60-69 year old age group; test for departure of trend (chi2=13, p=0.002). The incidence of new aneurysms was 3.5 per 1000 person-years (py) (95% CI: 2.8-4.4). The highest incidence of new aneurysms was found in the 60 to 69 year old age group.


CONCLUSIONS
only a small proportion of the population is prone to aortic dilatation. Patients over 70 with an IAD <2.5 cm can be discharged from follow-up.
Wilmink
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Department of Surgery, Norfolk & Norwich Hospital, Norwich, UK.
Hubbard
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Day
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Quick
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D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000473:pathology*; D017544:Aortic Aneurysm, Abdominal / Q000453:epidemiology*; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged