Prognosis of abdominal aortic aneurysms: A population-based study

Nevitt, Ballard, and Hallett reviewed the chans of virtually all known cases of abdominal aortic aneurysms in residents of Roch-ester, Minnesota, from 1951 to 1984.Of 370 patients included in this retrospective study, 181 had at least one ultrasound examina-tion; 103 of these had at least two. and 67 had three. Five patients who hadleakage or rupture of their aneurysm within 48 hours of their first ultrasound were excluded.The authors found that the median and mean increase in aneu-rysm size was 0.21cm and 0.26 cm per year, respectively. Therewere no cases of rupture in aneurysms less than 5.0 cm in diameter over the course of the study. Aneurysms which on presentation had a diameter of less than 3.5 cm. had a 0% incidence of ruptureat eight years. The risk of eventual rupture, following enlarge-ment, for aneurysms 3.5 to 4.9 cm at first ultrasound, was 5% at nine years. Of aneurysms greater than 5.0 cm at the outset, 25% had ruptured by eight years. No significant data regarding rate of change in size relative to risk of rupture were derived. The authors conclude that the rate of expansion of aneurysms is less than the accepted Figure of 0.4 cm per year, and that risk of rupture of aneurysms less than 5.0 cm in diameter is much smaller than believed. Because their study is based on a geographically defined rather than referral population. Nevitt et al assert that their data closely approximate the true natural history of abdominal aortic aneurysms.