Vasa Vasorum-A Silent Enemy After EVAR: A Case Report and Review of the Literature

Background/Objectives: Type II endoleaks (T2ELs) remain one of the most frequent causes of aneurysm sac enlargement following endovascular abdominal aortic aneurysm repair (EVAR). While embolization may be effective in typical T2ELs with a clearly identifiable feeding vessel, management becomes more challenging when no visible communication with a side branch can be demonstrated. Emerging evidence suggests that hypertrophic vasa vasorum may contribute to aneurysm sac expansion in these atypical cases. We present a case of refractory atypical T2EL treated by open conversion and discuss the potential role of the vasa vasorum network in its pathophysiology. Case Presentation: A 77-year-old man presented with lumbar pain ten years after EVAR for a symptomatic abdominal aortic aneurysm. Computed tomography angiography demonstrated progressive aneurysm sac enlargement to 8.5 cm despite three previous translumbar embolization procedures. Multiple areas of contrast pooling were identified within the aneurysm sac, but no clear communication with a feeding side branch was observed. Owing to persistent sac expansion and symptoms, open conversion was performed with partial endograft explantation and reconstruction using a bifurcated PTFE graft. Results: After opening the aneurysm sac and evacuating the thrombus, diffuse bleeding was observed from numerous small vascular orifices distributed throughout the inner sac surface. These findings were considered consistent with a prominent vasa vasorum network. Hemostasis was achieved using a combination of figure-of-eight sutures and electrocautery. The postoperative course was uneventful, and the patient was discharged on postoperative day five. Follow-up imaging demonstrated normal graft patency without complications. Conclusions: This case supports the hypothesis that an extensive vasa vasorum network may contribute to aneurysm sac expansion in atypical T2ELs and possibly endotension after EVAR. In patients with refractory sac enlargement, open conversion remains a definitive treatment option. Further research is needed to clarify the underlying mechanisms and to explore targeted therapeutic strategies aimed at modulating angiogenesis and vascular remodeling.