Surgery for small asymptomatic abdominal aortic aneurysms.

BACKGROUND: An aneurysm is an abnormal ballooning of an artery. One site in which this occurs is in the abdominal aorta, which is the major artery running through the abdomen. Some abdominal aortic aneurysms (AAA) present as an emergency and require surgery; others remain asymptomatic. Treatment of asymptomatic aneurysms depends on a number of factors, one of which is size. The risk of rupture increases with aneurysm size. Large asymptomatic aneurysms (>6 cm diameter) are operated on; small aneurysms (<4 cm diameter) have regular ultrasound to monitor growth.

OBJECTIVES: The objective of this review was to compare the mortality, quality of life and cost effectiveness of early surgical repair with routine ultrasound surveillance in patients with an AAA of between 4-6 cm diameter.

SEARCH STRATEGY: Trials were identified through searching the Cochrane Peripheral Vascular Diseases Group trials register and the reference lists of relevant articles. The reviewers also contacted investigators in the field and hand searched recent conference proceedings.

SELECTION CRITERIA: Randomised controlled trials in which men and women with asymptomatic AAA of diameter 4-6 cm were randomly allocated to early surgery, or ultrasound surveillance at least once every 12 months. Outcome measures had to include mortality, quality of life or financial costs.

DATA COLLECTION AND ANALYSIS: Data were abstracted by one reviewer and checked by others. Due to the small number of trials at present no tests of heterogeneity or sensitivity analyses were performed.

MAIN RESULTS: Only one trial, the UK Small Aneurysm Trial, fulfilled the criteria for inclusion. This trial found no differences in mortality between the early surgery and surveillance groups at two, four and six years following randomisation (six years Peto OR 1.01 [95% CI 0.77-1.31]). Mean health service costs were higher in the surgery than the surveillance group, difference 1,064 pounds per patient [95% CI 796-1332]. Quality of life remained similar in the two groups but early surgery patients thought they were healthier and had less pain one year after randomisation. There were not enough patients in the trial to allow analysis of subgroups by, for example, age or aneurysm size.

REVIEWER'S CONCLUSIONS: The results from the one trial to date indicate that patients with asymptomatic AAA of 4-5.5 cm should normally have regular ultrasound surveillance accompanied by surgical intervention for aneurysms which grow rapidly (>1 cm per year) or reach 5.5 cm. The results are awaited of a major trial in progress in the USA.