Endovascular abdominal aortic aneurysm repair: surveillance of endoleak using maximum transverse diameter of aorta on non-enhanced CT

Background. Repeat volumetric analysis of abdominal aortic aneurysm (AAA) after endovascular AAA repair (EVAR) is time-consuming and requires advanced processing, dedicated equipment, and skilled operators. Purpose. To clarify the validity of measuring the maximal short-axis diameter (Dmax) of AAA in follow-up non-enhanced axial CT as a means of detecting substantial endoleaks after EVAR. Material and Methods. CT images were retrospectively reviewed in 47 patients (7 women, 40 men; mean age, 76.2 years) who had no endoleak on initial contrast-enhanced CT after EVAR. Regular follow-up CT studies were performed every 6 months. At each CT study, the Dmax on the CT axial image was measured and compared with that on the last CT (115 data-sets). Contrast-enhanced CT was regarded as the standard of reference to decide the presence or absence of endoleaks. The appearance of endoleak was defined as the end point of this study. Results. Endoleaks were detected in 17 patients during the follow-up period. Mean Dmax changes for 6 months were significant between positive and negative endoleak cases (1.8 ± 1.9 vs. -1.1 ± 3.0 mm, P < 0.0001). When the Dmax change ≤ 0 mm for 6 months was used as the threshold for negative endoleak, the sensitivity, specificity, positive predictive value, and negative predictive value were 74.5, 82.4, 96.1, and 35.9%, respectively. When Dmax change ≤-1 mm was used as the threshold, the sensitivity, specificity, PPV, and NPV were 38.8, 100, 100, and 22.1%, respectively. Conclusion. Contrast-enhanced CT is not required for the evaluation of endoleaks when the Dmax decreases by at least 1 mm over 6 months after EVAR