Observational Study Comparing the Measurement of Abdominal Aortic Aneurysm (AAA) Diameter in Different Morphology with Ultrasound and CT Scan PC05-PC07
Dr. Ahmed Shalan,
Department of Vascular Surgery, York Teaching Hospital, York, YO318HE.
Introduction: Ultrasound (US) is the gold standard imaging modality used to measure the diameter of Abdominal Aortic Aneurysms (AAA), and it is used in the surveillance of AAAs. The use of Computed Tomography (CT) has now become widespread. There has always been disagreement between CT and US, which significantly affects management decisions.
Aim: To examine the agreement between US and CT in measuring aortic diameter. Furthermore, it was used to investigate if size discrepancy between US and CT increases as the AAA size increases.
Materials and Methods: This was a single centre retrospective observational study. It included 212 patients, with infra-renal aorta of diameters =3 cm, who had undergone an US of the aorta and a CT aortogram within 90 days of each other. US-measured maximum Antero-Posterior (AP) aortic diameter and CT-measured maximum aortic diameter were considered. Statistical analysis was performed using Bland-Altman plot, paired t-test and Pearsonís correlation.
Results: There was a significant disagreement between measurements on CT and US. The mean US measured AP diameter was 5.4 cm (SD1.05), whereas the mean maximum measured aortic diameter on CT was 5.7 cm (SD1.13) (p<0.001). We did not find any disagreement between US and CT as the size of the AAA increased, with significant but weak correlation (cc 0.27) (p<0.001).
Conclusion: Our results demonstrate that US, on average, underestimates the size of AAAs by 0.3 cm when compared to CT. We failed to demonstrate correlation between increasing aneurysm size and increasing disagreement between CT and US.