Abstract Body (Do not enter title and authors here): Introduction: Type III endoleaks are a significant complication following endovascular aneurysm repair (EVAR) for abdominal aortic aneurysms (AAAs). They are characterized by persistent blood flow into the aneurysm sac due to structural defects in the endograft - either component separation (Type IIIa) or fabric disruption (Type IIIb). Incidence varies by device and study but generally ranges between 2% - 4%.

Case Presentation: A 96-year-old female with a history of nonobstructive CAD, sinus bradycardia, HTN, and an infrarenal AAA s/p recent EVAR, presented with constant, non-radiating lower abdominal pain for approximately 1.5 weeks. The pain had worsened and resembled the discomfort experienced prior to her initial AAA diagnosis. Vitals were BP 149/54, HR 58, and SpO2 95%. Labs remarkable for Hgb 10.9 (at baseline), Cr 1.6, troponin 7, and lactic 1.2. CTA revealed a stable aneurysm sac measuring 5.7cm, but a hyperdensity anterior to the proximal iliac stents raised concern for possible Type III endoleak. No feeding vessels were seen to suggest a Type II endoleak. The patient was taken to the cath lab for further evaluation and potential intervention. Intra-procedural aortography demonstrated a widely patent endograft with no evidence of Type I, II, or III endoleak, despite multiple angiographic projections. However, due to the concerning CTA and ongoing symptoms, an additional endoprosthesis was deployed across the entire right iliac limb. Her symptoms resolved postoperatively, and she was discharged home in stable condition.

Discussion: Type III endoleaks necessitate prompt intervention due to their strong association with aneurysm rupture and increased long-term mortality. The 5-year survival rate for patients with post-EVAR Type III endoleaks is approximately 66%, compared to 84% in patients without endoleaks. Endovascular repair remains first-line treatment, typically involving relining the affected segment with additional stent grafts or using endovascular sealing techniques. While both CTA and conventional angiography have high sensitivity and specificity, angiography may detect endoleaks missed or misclassified by CTA. This case illustrates the diagnostic challenges posed by occult or intermittent endoleaks. Despite the absence of angiographic confirmation, empiric intervention led to symptom resolution, emphasizing the importance of clinical judgment when imaging and procedural findings are discordant.