Results
Technically there was no inadequate CDUS examination. There were 11 detected endoleaks (13.1%) with CTA and 7 with CDUS (8.3%). There was one type IA, three type IB, two type III and five type II endoleaks detected with CTA (Table 2). CDUS was not able to detect four type II endoleaks, however, all type I and III endoleaks were detected. Figure 1-4 demonstrate the type I and III endoleaks in Blood flow image(BFi) and Color Doppler modes. Among the modes of CDUS, eventhough BFi was much more demonstrable, there was no superiority or sensitivity difference. There were no leaks missed on CDUS requiring intervention however, there was an insufficiency of CDUS in detecting low flow. Eliminating this frailty, there was a very high correlation of aneurysm sac diameter measurement between CTA and CDUS. For CDUS average aneurysm sac diameter was 57.1±14.5 mm, for CTA 58.7±15.0 mm. There was a very strong correlation of CTA and CDUS for diameter measurement and endoleaks (r = 0.884 and r = 0.777 respectively, p < 0.001 for both).
The mean difference from Bland-Altman analysis (Figure 5) was 1.5 ± 2.2 mm and limits of agreement were -2.85 mm (lower limit) and 5.93 mm (upper limit). A small percentage of measurements were outside of the ± 2 SD ranges. The direction and magnitude of the mean differences were similar between the two methods of measurement (CDUS and BTA). Linear regression analysis represented no proportional bias (p=0.233).
The sensitivity and specificity of CDUS was 63.6% and 100% respectively. The accuracy was 95.2%. Positive and negative predictive values were 100% and 94.8% respectively. The missed type II endoleaks were not considered to be clinically significant. They are still under follow up for sac enlargement. The detected type II endoleak was written as “suspected endoleak” because of a mobile thrombus seen inside the aneurysm sac.