The goal of this clinical trial is to learn if the Fenestrated TREO Stent-Graft System works to treat abdominal aneurysms in adults. An abdominal aneurysm is a bulge in the main blood vessel (the aorta) which carries blood from the heart, through the chest and abdomen. It will also learn about the safety of Fenestrated TREO Stent-Graft System.

The main question it aims to answer is: Can the the Fenestrated TREO Stent-Graft System be used to treat participants with a specific type of abdominal aneurysm called a juxtarenal abdominal aortic aneurysm?

Participants will: Have the the Fenestrated TREO Stent-Graft System implanted via an endovascular surgical procedure and visit the hospital for a follow up period of 5 years, for checkups, tests and imaging scans.

Inclusion Criteria:

• 18 years or older at the time of consent

• Life expectancy is greater than 2 years

• An abdominal aortic or aorto-iliac aneurysm requiring a fenestrated graft and with morphology suitable for endovascular repair (confirmed by Computed Tomography (CT) with contrast performed within 6 months of planned implant procedure) as follows:

  1. Maximum aneurysm diameter of ≥5.5 cm for male ( ≥5.0 cm for female) or
  2. Maximum AAA diameter exceeding two times the normal diameter just proximal to the aneurysm using orthogonal (i.e., perpendicular to the centerline) measurements (or saccular aneurysm that warrants treatment in the opinion of the investigator) or
  3. Aneurysm with a history of growth > 0.5 cm in 6 months and
  4. Minimum 0 mm of healthy aorta* below the most inferior renal artery that the physician plans on preserving and no renal artery involvement (juxtarenal aneurysms) or
  5. At least one renal artery involved in the aneurysm and minimum 2 mm below the celiac (suprarenal aneurysms) *Healthy aorta is defined as segment of aorta with parallel aortic wall with minimal (<10%) or no difference in diameter and minimal atherosclerotic debris, thrombus, or calcification.

• Proximal landing zone:

  1. ≥20 mm length
  2. 20-32 mm diameter
  3. ≤60° angle relative to the axis of the suprarenal aorta
  4. ≤60° angle relative to the long axis of the aneurysm

• Distal (iliac) landing zone with:

  1. 8-13 mm inside diameter/ ≥10 mm length
  2. >13-20 mm inside diameter/ ≥15 mm length

• Distal aortic diameter (above the iliac bifurcation) ≥70% of the sum of the iliac limb graft diameters

• Minimum 18 mm aortic lumen diameter at the level of the fenestrations

• Pathology that requires maximum 5 fenestrations in the main body

• Pathology that requires fenestration a minimum 3 mm apart (edge to edge)

• Branch vessels (to be bridged to the fenestrated graft) with:

  1. 5-9 mm diameters
  2. ≥13 mm distal landing zone (or ≥15 mm if there is a gap between fenestration and target vessel)

• Adequate renal function to tolerate contrast-enhanced CTA

• Adequate vascular access compatible with required delivery systems

• Willingness to comply with the follow-up evaluation schedule documented in a signed informed consent prior to implant

Exclusion Criteria:

• Pregnant or lactating

• Existing endovascular graft in the treated segment intended to be repaired with the Fenestrated TREO Stent-Graft System

• Dissection in abdominal aorta, ruptured aneurysm, or symptomatic aneurysm (as determined by treating physician)

• Implant procedure as planned does not allow for at least one patent hypogastric artery left intact, unless both are occluded on pre-op imaging.

• A branch vessel(s) that is dissected or has significant calcification, tortuosity, thrombus formation that would interfere with bridging stent delivery or sealing (as determined by treating physician)

• Severe untreated coronary artery disease and/or unstable angina, significant areas of myocardium at risk (based on coronary angiogram or radionuclide scans), left ventricular ejection fraction <20%, or recent diagnosis of congestive heart failure (CHF; as determined by treating physician).

• Stroke or myocardial infarction within 6 months of the planned treatment date

• Chronic obstructive pulmonary disease requiring routine need for oxygen therapy outside the hospital setting (e.g., daily or nightly home use)

• Chronic Kidney Disease (CKD) stage ≥3b.*

  * During Stage 2, patients with severe CKD (stage ≥3b) can be included in the Expanded Access Arm if otherwise eligible.

• Active systemic infection or is suspected of having an active systemic infection (e.g., acquired immune deficiency syndrome (AIDS)/human immunodeficiency virus (HIV), sepsis)

• Clinical conditions that would severely compromise or impair x-ray visualization of the aorta (as determined by treating physician).

• History of an aortopathic connective tissue disease (e.g., Marfan's syndrome)

• Mycotic aneurysm

• Significant or circumferential calcification or mural thrombus (as determined by treating physician):

  1. in the proximal aortic neck
  2. in the distal iliac landing zone
  3. within the treatment length, which may adversely impact device patency

• Cannot receive intraprocedural anticoagulation per the investigator's standard of care, or antiplatelet therapy post-procedurally as per the investigator's standard of care.

• Blood coagulation disorder or bleeding diathesis, the treatment for which cannot be suspended pre- and post-repair

• An investigational study drug or biologic within 30 days of planned procedure or an investigational device within one year of planned procedure or any other treatment that may interfere with the interpretation of the study results.

• Medical, social or psychological issues that the investigator believes may interfere with study treatment or follow-up.

• Untreatable allergy or sensitivity to contrast media, nitinol/nickel, Tantalum, Platinum Iridium (PtIr), 316 stainless steel, ePTFE (expanded polytetrafluoroethylene), PTFE (polytetrafluoroethylene) Impregnated polyester fiber, or polyester

• Other major surgical or medical intervention within 45 days of the planned procedure or plan to undergo other major surgical or medical intervention within 45 days post implantation (e.g., coronary artery bypass graft (CABG), organ transplantation, renal stenting)

Publications and presentations referring to the study will be coordinated by a Study Publication Committee overseen by the Sponsor. This committee will be responsible for the following activities: determining the scope of each publication; reviewing data provided by the Biostatistician; writing scientific papers or preparing presentation; submitting papers for publication or abstracts for conference/congress presentations. Decisions on IPD sharing will be taken as part of the study publication process.