The goal of this observational study is to find out what factors contribute to a good treatment outcome in patients who have received a stent for their dilation of the main abdominal artery (abdominal aortic aneurysm or AAA). The primary goal of this study is to build a prediction model for abdominal aortic aneurysm shrinkage one year after the treatment.

Inclusion Criteria:

• Age ≥ 18 years;
• Elective, initially technically successful (as described by the ESVS guidelines11), infrarenal EVAR for unruptured infrarenal AAA;
• Implanted endograft is a Gore Excluder, Medtronic Endurant, Cook Zenith, Cordis Incraft, Endologix AFX, Jotec E-Tegra, or Vascutek Anaconda endograft;
• Follow-up of the AAA of at least one year with imaging of the same modality as the preoperative imaging;
• Axial reconstructions of preoperative CT angiography available, preferably in the arterial phase and with 3 mm or smaller slice thickness.

Exclusion Criteria:

• Patients with ruptured or symptomatic AAA;
• Patients that were treated with fenestrated or branched endografts, iliac branched devices, non-CE marked devices within trial setting, other endografts (EVAS cases) or chimney procedures;
• Acute procedures;
• Reintervention before one year follow-up;
• Revision cases after previous open or endovascular aneurysm repair of an AAA;

Patients, electively treated with EVAR for an infrarenal AAA, will be included from the hospital records of 5 experienced vascular centers, 4 sites in the Netherlands and 1 site in Sweden.