Aneurysm Sac Expansion After EVAR: Associated Factors, Prognostic Impact, and Preventive Strategies—A Systematic Review and Meta-Analysis

Background/Objectives: Aneurysm sac expansion is an adverse marker of durability after endovascular aneurysm repair (EVAR). We assessed factors associated with expansion, its prognostic significance, and the effect of preventive embolisation. Methods: PubMed/MEDLINE, Web of Science, and Scopus were searched through 23 August 2026 (PROSPERO CRD420261386132). Random-effects meta-analyses analysed odds ratios (ORs), hazard ratios (HRs), and risk ratios (RRs) separately; risk of bias and certainty were assessed with RoB 2, ROBINS-I, QUIPS, and GRADE. Results: Thirty-three reports (20 independent quantitative studies) were included. Type II endoleak (OR 5.16, 95% confidence interval [CI] 2.53–10.50; HR 3.08, 95% CI 2.11–4.49) and type I endoleak (OR 11.94, 95% CI 5.30–26.90) were associated with expansion (low certainty). Expansion was associated with higher late mortality in a single independent adjusted cohort (HR 1.31, 95% CI 1.14–1.51; very low certainty). Preventive embolisation was associated with lower risks of persistent type II endoleak (RR 0.58, 95% CI 0.34–0.97; low certainty) and reintervention (RR 0.44, 95% CI 0.24–0.82; very low certainty), but neither association remained statistically conclusive in sensitivity analyses. Conclusions: Endoleaks are consistently associated with sac expansion, which appears to identify patients at increased late risk. Effects of preventive embolisation on surrogate outcomes are not robust; prevention of sac expansion and clinical events is unproven.