Recommendations for screening intervals for small aortic aneurysms

BACKGROUND: The aim was to determine the optimum rescreening interval for small abdominal aortic aneurysms (AAAs). METHODS: Data from 12 years of population screening of 65-year-old men were analysed and 1121 small AAAs (less than 4.0 cm in initial diameter) were divided into groups: group 1 (2.6-2.9 cm; n = 625), group 2 (3.0-3.4 cm; n = 330) and group 3 (3.5-3.9 cm; n = 166). Expansion rate and the cumulative proportions to expand to over 5.5 cm, or require surgery, or rupture were calculated. RESULTS: Expansion rate was related to initial aortic diameter: 0.09 cm per year in group 1, 0.16 cm per year in group 2 and 0.32 cm per year in group 3 (P < 0.001). Aneurysms in 2.4 per cent of patients in group 1 exceeded a diameter of 5.5 cm or required surgery within 5 years; there were no ruptures. In group 2, no aorta exceeded 5.5 cm but at 3 years 2.1 per cent had reached 5.5 cm and 2.9 per cent had required surgery. The rupture rate at 3 years was zero. In group 3, the aneurysm diameter exceeded 5.5 cm in 1.2 per cent of patients, but no patient required surgery or experienced rupture within 1 year; at 2 years 10.5 per cent of aneurysms had exceeded 5.5 cm in diameter or required surgery and 1.4 per cent had ruptured. CONCLUSION: The appropriate rescreening interval can be determined by initial aortic diameter in screened 65-year-old men. AAAs of initial diameter 2.6-2.9 cm should be rescanned at 5 years, those of 3.0-3.4 cm at 3 years and those of 3.5-3.9 cm at 1 year.