[Criteria for quantification and characterization of aneurysms of the abdominal aorta using ultrasonography. The AFFCA study. French Association of Continuous Education in Angiology].

Objective: To validate ultrasonographic quantification and characterization criteria for aneurysms of the abdominal aorta (AAA) by comparing computed tomography data and surgical findings in order to standardize diagnosis and follow-up of AAA.
Patients and Methods: A multicentric prospective study included 80 patients with AAA (January to August 1996). Standardized data on quantitative (diameter, surface area) and qualitative (topography, form, wall, thrombus) data were obtained at each ultrasound examination and at surgery. Ultrasound (US) and computed tomography (CT) explorations were performed and interpreted without prior knowledge by independent operators. US findings versus CT reference were compared in 77 cases, US findings versus surgical reference in 31, and CT findings versus surgery reference in 28.
Results: Compared with CT-scan, B mode ultrasound (n = 77) underestimated the anteroposterior diameter of the aneurysm (mean difference -2.16 mm; p < 0.001), the anteroposterior diameters of the flow channel lumen (-5.54 mm; p < 0.001) and upper neck of the aneurysm (-2.74 mm; p < 0.001). Surface area measurements were not significantly different both the aneurysmal sac (p = 0.3) and the flow channel lumen (p = 1). Compared with surgical findings, US (n = 30) underestimated the transverse diameter (mean difference (-4.29 mm; p = 0.0037). Compared with surgery, US findings (n = 28) were not significantly different for the anteroposterior ans transverse diameters. Analyzing the form and wall of the AAA, US/CT-scan performance was good for symmetrical fusiform aneurysms (sensitivity 77%, specificity 67%). US and CT-scan were reliable for detecting wall bugles (same sensitivity, 29%). The angle formed by the thrombus with the wall (expressed in degrees) was not significantly different (p = 0.9). When the lower pole of the aneurysm was situated above the aortic bifurcation, US (sensitivity 75%) was more reliable than the CT-scan (sensitivity 50%) compared with surgical findings.
Conclusion: Ultrasonography should not be limited to the simple positive diagnosis of AAA. A precise analysis of the diameters and surface areas of the aneurysm should be performed.