Volumetric Analysis versus Diameter Measurement for Early Detection of Post-EVAR Sac Progression

Objective To compare diameter- and volume-based surveillance after endovascular aneurysm repair (EVAR) and determine whether volumetric sac assessment identifies postoperative remodeling not captured by conventional maximum diameter measurement. Methods This retrospective single-center study included 383 patients who underwent elective EVAR for infrarenal abdominal aortic aneurysm between January 2016 and April 2024. All patients had preoperative and postoperative computed tomography angiography and at least 1 year of follow-up. Maximum sac diameter, total aneurysm sac volume, thrombus volume, thrombus density, neck morphology, and other anatomical variables were assessed using standardized morphometric and three-dimensional morphovolumetric measurements. Sac dynamics were classified by diameter criteria (≥5 mm decrease, stable, or ≥5 mm increase) and volumetric criteria (>10% decrease, stable, or >10% increase). Results Endoleaks occurred in 26.1% of patients (n = 100), and secondary interventions were required in 14.1% (n = 54), with a mean time to reintervention of 21.7 ± 10 months. At final follow-up, 74.7% demonstrated sac diameter reduction, 18.5% were stable, and 6.8% had enlargement, whereas volumetric analysis showed shrinkage in 81.7%, stability in 6.0%, and enlargement in 12.3%. At 1, 6, and 12 months, cohort mean diameter changed by −0.6%, −3.1%, and −6.5% from baseline, respectively, while cohort mean volume changed by −0.5%, −5.7%, and −12.5%. Among diameter-stable sacs, 32.4% enlarged volumetrically and 38.0% regressed volumetrically. In enlarging sacs, a 10% volume increase corresponded to an approximately 4 mm diameter increase (R 2 = 0.72; P < 0.001); this 4 mm value was a regression estimate, not the diameter threshold used for sac classification. Preoperative morphometric and morphovolumetric variables were associated with endoleak and secondary intervention in exploratory analyses. Conclusion Volumetric sac analysis identified additional postoperative remodeling beyond maximum diameter measurement, particularly in apparently stable sacs. A practical surveillance strategy combining rapid diameter-based screening with selective volumetric analysis in stable, borderline, or clinically suspicious cases may improve recognition of adverse sac behavior without requiring routine volumetry in every follow-up study.