The role of the aortic aneurysm diameter aortic diameter ratio in predicting the risk of rupture.

This study was performed to examine the ratio between the size of an infrarenal aortic aneurysm and the normal aorta proximal to it, in the hope of identifying a high-risk group of patients. All patients underwent a computed tomography scan of the abdomen, at which time the diameters of the largest aneurysm and of the normal proximal aorta were measured. The ratio was calculated by dividing the diameter of the normal aorta (in centimetres) into the diameter of the aneurysm. One hundred and thirty patients were assessed. One hundred asymptomatic patients had a mean ratio of 2.0. The 30 symptomatic patients were subdivided into 2 groups; 17 were symptomatic but had no evidence of rupture (mean ratio 2.7), and the remaining 13 had a contained rupture (mean ratio 3.4). There was a significant difference between the asymptomatic patients and the two symptomatic groups (P less than 0.001). The results suggest that the aneurysm/aorta ratio may be helpful in identifying the high-risk aneurysm. Patients with a ratio of 2.7 or greater are likely to become symptomatic, whereas those with a ratio of 3.4 or greater are at risk of rupture.