An aneurysm is a ballooning of an artery (blood vessel), which can happen in the major artery in the abdomen (aorta). The cause is unknown. Ruptured aneurysms cause death unless surgical repair is rapid, which is difficult to achieve. Surgery for patients with aneurysms more than 5.5 cm in diameter or who have associated pain is considered necessary to relieve symptoms and to reduce the risk of rupture and death, although there are risks associated with surgery. Surgical repair of the aneurysm consists of insertion of a prosthetic inlay graft either by open surgery or endovascular repair.
Small asymptomatic abdominal aortic aneurysms are at low risk of rupture. They are monitored through regular imaging so they can be surgically repaired if they subsequently enlarge.
This review identified four well-conducted, controlled trials that randomised 3314 patients with small (diameter 4.0 to 5.5 cm) asymptomatic aneurysms in the abdominal aorta to immediate repair or regular, routine ultrasounds to check for aneurysm growth ('surveillance'). Among the patients randomised to surveillance, the aneurysm was repaired if it was enlarging, reached 5.5 cm in diameter, or became symptomatic The trials did not show a meaningful difference in long-term survival between immediate repair and selective surveillance over the 3 to 10 years of follow-up. The four trials showed an early survival benefit in the surveillance group because of the number of deaths within 30 days of surgery (operative mortality). Some 31% to 75% of the participants randomised to surveillance eventually had the aneurysm repaired.
The results from the four trials conducted to date suggest no overall advantage to early surgery for small abdominal aortic aneurysms (4.0 to 5.5 cm). The findings do not allow additional guidance for 'best-care' management of subgroups of patients (based, for example, on age, gender, or aneurysm diameter) since the trials did not provide data allowing analysis of results in these subgroups. This is in relation to the intervention versus control and the specified end-points. Furthermore, the more recent trials focused on the efficacy of endovascular aneurysm repair and still failed to show a benefit. Thus, both open and endovascular repair of small abdominal aortic aneurysms are not supported by currently available evidence.