Randomized control trials have shown that the risk of rupture of small (<5 cm) abdominal aortic aneurysm is quite low, and that a policy of careful surveillance up to a diameter of 5.5 cm is safe, unless rapid expansion (>1 cm/y) or symptoms develop. However, early surgery is comparable to surveillance with later surgery, so that patient preference is important, especially for abdominal aortic aneurysm 4.5 cm to 5.5 cm in diameter. Based upon the best available current evidence, 5.5-cm diameter appears to be an appropriate threshold for repair in an "average" patient.

However, subsets of younger low-risk patients, with long projected life- expectancy, may prefer early repair. If the surgeon's personal documented operative mortality rate is low, repair may be indicated at smaller sizes (4.5-5.5 cm) if that is the patient's preference. For women, or abdominal aortic aneurysm with greater than average rupture risk, elective repair at 4.5 cm to 5.0 cm is an appropriate threshold for repair, and for high-risk patients, delay in repair until larger diameter is warranted, especially if endovascular aneurysm repair is not possible.

In view of its uncertain long-term durability and effectiveness, as well as the increased surveillance burden, endovascular aneurysm repair is most appropriate for patients at increased risk for conventional open aneurysm repair. Endovascular aneurysm repair may be the preferred treatment method for older, high-risk patients, those with "hostile" abdomens, or other clinical circumstances likely to increase the risk of conventional open repair, if their anatomy is appropriate, use of endovascular aneurysm repair in patients with unsuitable anatomy markedly increases the risk of adverse outcomes, need for conversion to open repair, or abdominal aortic aneurysm rupture. At present, there does not appear to be any justification that endovascular aneurysm repair should change the accepted size thresholds intervention in most patients. In choosing between open repair and endovascular aneurysm repair, patient preference is of great importance. It is essential that the patients be well informed to make such choices.