Pre-operative evaluation of abdominal aortic aneurysms: ultrasound or computed tomography?

Evaluation of aortic aneurysms by ultrasound (US) or computed tomography (CT) is now commonplace and their use often reflects personal preferences given their similar diagnostic accuracy. Knowledge of anatomic details may be very helpful in the planning of the surgical procedure. Involvement of the supra-renal aorta, relative position of the renal arteries, intra-aneurysmal thrombus, and extension to the iliac arteries were retrospectively evaluated by both techniques to determine which modality was more valuable in the preoperative evaluation of abdominal aortic aneurysms. A group of 58 patients was reviewed. An infra-renal aortic aneurysm was identified in all instances by both methods. The supra-renal aorta was always well visualized by CT but not by US. The origin of at least one renal artery was seen in only 11% of the cases by US but in 100% by CT. CT demonstrated the left renal vein in all cases, while only 41% were demonstrated by US. Intra-aneurysmal thrombus was depicted by both methods but its distribution within the sac and the characteristics of the thrombus were apparent on CT but not on US. Aneurysmal involvement of the iliac arteries was present in 19% of the patients. CT detected all cases but only 14% were demonstrated by US. Both methods accurately diagnose abdominal aortic aneurysms. Supplementary data regarding proximal and distal extension, characteristics of the thrombus, relationship to the renal vessels, and adjacent major veins can be obtained by CT and usually not by US. This information is of value in the planning and execution of the indicated surgical procedure.