CT after Endovascular Repair of Abdominal Aortic Aneurysms: Diagnostic Accuracy of Diameter Measurements for the Detection of Aneurysm Sac Enlargement.

PURPOSE: To evaluate the diagnostic accuracy of diameter measurements for the detection of aneurysm volume increase during follow-up after endovascular aortic repair (EVAR) of abdominal aortic aneurysms (AAAs).

MATERIALS AND METHODS: This retrospective study analyzed 100 pairs of follow-up computed tomography scans randomly selected from an EVAR database (male/female ratio, 91/9; mean age, 71 y; bifurcated and aortouniiliac stent grafts, 96% and 4%, respectively; mean interval, 359 d). Five maximum diameter (Dmax ) values were measured (anteroposterior, transverse, axial, coronal, and perpendicular). Aneurysm sac volume was measured by manual segmentation and used as the standard of reference. Overall, 37% of patients had a persistent type II endoleak.

RESULTS: The anteroposterior, transverse, axial, coronal, and perpendicular Dmax values increased in 39 patients (mean, 4.3 mm), 30 patients (mean, 4.0), 35 patients (mean, 3.9 mm), 43 patients (mean, 3.9 mm), and 41 patients (mean, 4.3 mm), respectively. Aneurysm sac volume increased in 39 patients (mean, 25.7 cm3 ). The cutoff levels according to the reporting standard for aneurysm sac enlargement (diameter ≥ 5.0 mm, volume ≥ 5.0%) had sensitivity/specificity rates of 29%/95%, 33%/97%, 29%/99%, 33%/93%, and 38%/96%, respectively, for the five Dmax values. The reference standards failed to detect aneurysm volume increase in 72%, 67%, 72%, 61%, and 67% of patients, respectively, with persistent type II endoleak.

CONCLUSIONS: Depending on the chosen cutoff value, diameter measurements showed low to moderate sensitivity for the detection of aneurysm volume increase. The diameter measurements failed to detect aneurysm enlargement in a large number of patients with persistent type II endoleak after EVAR of AAA.