Pre-emptive embolization of aneurysm sac side branches in endovascular aneurysm repair: A systematic review and meta-analysis

Background: Pre-emptive side branch embolization (PBE), typically targeting the inferior mesenteric artery (IMA) or lumbar artery during endovascular aneurysm repair, usually aims to prevent type II endoleaks (T2ELs), but its true role remains unclear. This study evaluates the impact of PBE on sac dynamics, aneurysm-related reinterventions, T2EL incidence, rupture, and mortality. Methods: We conducted a systematic review and meta-analysis of studies assessing the effect of PBE during endovascular aneurysm repair. PubMed, EMBASE, and Cochrane were searched up to February 2026. Outcomes included T2EL and type I endoleak incidence, aneurysm-related reinterventions, sac growth and shrinkage, rupture, and mortality. Temporal subgroups were analyzed at 6 months and 3 years. Subgroup analysis was conducted on studies that restricted embolization to IMAs ≥ 2.5 mm. Data were analyzed using RevMan Web. Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed. Results: Twenty-two studies including 19,433 patients and two randomized controlled trials were analyzed (18% female, 80% current or former smokers, and 19% diabetic). Among these, 1950 (10%) underwent PBE, which was associated with reduced T2EL incidence at last follow-up [risk ratio (RR), 0.62; 95% confidence interval (CI), 0.46-0.84; P = .003], and aneurysm-related reinterventions (RR, 0.58; 95% CI, 0.38-0.89; P = .02). It was also associated with reduced sac enlargement ≥ 5 mm (RR, 0.49; 95% CI, = 0.31-0.77; P = .005), and increased sac shrinkage ≥ 5 mm (RR, 1.31; 95% CI, 1.02-1.68; P = .04; I2 = 62%), but did not significantly impact type I endoleak (RR, 0.81; 95% CI, 0.46-1.40; P = .36). Procedural and fluoroscopy times, as well as contrast volume, were higher with PBE (+28 and +16 min; +28 mL). Time-stratified analysis showed no effect on 6-month T2EL incidence (RR, 0.61; 95% CI, 0.27-1.36; P = .18), but a significant reduction with ≥3-year follow-up (RR, 0.43; 95% CI, 0.24-0.80; P = .02). In the subgroup of studies restricting embolization to IMAs ≥ 2.5 mm, the analyses revealed an association with reduced T2ELs (RR, 0.50; 95% CI, 0.26-0.95; P = .04), but no effect on sac growth ≥ 5 mm (RR, 0.38; 95% CI, 0.13-1.12; P = .06). No difference in rupture rates (RR, 0.77; 95% CI, 0.15-3.96; P = .56) or mortality (RR, 0.58; 95% CI, 0.31-1.07; P = .07) was observed. Conclusions: PBE may be associated with reduced long-term T2EL incidence, sac expansion, and reinterventions, while possibly improving sac shrinkage. However, current evidence does not support a benefit on hard clinical outcomes, including aneurysm rupture or mortality. Its routine use cannot be recommended, and future randomized trials with follow-up beyond 5 years and standardized reporting are essential to clarify its clinical utility.