Multidetector CT in abdominal aortic aneurysm treated with endovascular repair: are unenhanced and delayed phase enhanced images effective for endoleak detection?

To retrospectively determine the sensitivity and specificity of unenhanced, delayed enhanced phase (DEP), and arterial enhanced phase (AEP) multi– detector row computed tomog- raphy (CT) for depicting endoleaks during follow-up of endo- vascular aneurysm repair. Fifty patients (two women, 48 men; mean age, 72 years) underwent follow-up multi–detector row CT 1, 6, and 12 months after endovascular aneurysm repair. Unenhanced CT was performed with 2.5-mm collimation; 1-mm collimation was used with AEP and DEP examinations. Two independent readers assessed the presence of endoleak in three reading sessions: AEP (session A), unenhanced and AEP (session B), and AEP and DEP (session C). At 6- and 12-month follow-up, a fourth set was included: 1-month unenhanced and AEP (session D). Sensitivity, specificity, and positive predictive value of each session were calculated. Triple-phase multi– detector row CT was the reference standard. At 1 month, sensitivity, specificity, and positive predictive value, respectively, were 79%, 75%, and 55% for session A; 93%, 97%, and 93% for session B; and 93%, 78%, and 62% for session C. At 6 months, sensitivity, specificity, and posi- tive predictive value, respectively, were 92%, 68%, and 48% for session A; 92%, 100%, and 100% for session B; and 100%, 84%, and 67% for session C. At 12 months, sensitiv- ity, specificity, and positive predictive value, respectively, were 80%, 80%, and 50% for session A; 90%, 98%, and 90% for session B; and 100%, 80%, and 56% for session C. Sensitivity did not significantly differ (P .05) among reading sessions A, B, and C, whereas specificity and positive predic- tive values in session B were significantly higher (P .001). For 6- and 12-month follow-up, no significant differences (P .05) were found between sessions D and B. The combination of AEP and unenhanced imaging per- formed at 1-month follow-up offers improved specificity and positive predictive values compared with AEP alone. DEP imaging does not significantly increase sensitivity for detection of endoleaks, but it does depict low-flow en- doleaks not seen at AEP.