Surgery for small abdominal aortic aneurysms that do not cause symptoms

Cochrane: An aneurysm is a ballooning of an artery (blood vessel), which, in the case of an abdominal aortic aneurysm (AAA), occurs in the major artery in the abdomen (aorta). Ruptured AAAs cause death unless surgical repair is rapid, which is difficult to achieve. Surgery is considered necessary for people with aneurysms of more than 5.5 cm in diameter or who have associated pain, to relieve symptoms and to reduce the risk of rupture and death. However, risks are associated with surgery. Surgical repair consists of insertion of a prosthetic inlay graft, either by open surgery or endovascular repair.

Small asymptomatic AAAs are at low risk of rupture and 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 participants with small (diameter 4.0 cm to 5.5 cm) asymptomatic AAAs 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 four trials showed an early survival benefit in the surveillance group because of the number of deaths within 30 days of surgery (operative mortality). The trials did not show a meaningful difference in long-term survival between immediate repair and selective surveillance over the three to eight years of follow-up. Some 31% to 75% of the participants randomised to surveillance eventually had the aneurysm repaired. Overall, the risk of bias within the included studies was low and the quality of the evidence high. The results from the four trials conducted to date suggest no overall advantage to immediate surgery for small AAAs (4.0 cm to 5.5 cm). A pooled analysis of the two trials comparing immediate open surgical repair to surveillance demonstrated that this result holds true regardless of patient age or aneurysm size (within the range of 4.0 cm to 5.5 cm diameter). Furthermore, the more recent trials, which focused on the efficacy of endovascular repair, also failed to show a benefit over surveillance. Quality-of-life results among trials were conflicting. Thus, neither immediate open nor immediate endovascular repair of small AAAs is supported by the current evidence.