Abdominal Aortic Aneurysm Types Abdominal aortic aneurysm (AAA) is a common vascular lesion in the elderly, often caused by atherosclerosis. Siegfried classified three types of AAA according to their relationship with the renal artery: suprarenal: AAA affecting the opening of the renal artery or above; renal: AAA within 15 mm below the renal artery; and infrarenal: AAA more than 15 mm below the renal artery. Type A: AAA distal and proximal neck length ≥10 mm, diameter ≥25 mm. Type B: AAA proximal neck length ≥10 mm, diameter ≥25 mm, and aneurysm does not enter the aortic bifurcation. Type C: The proximal neck of the AAA is ≥10 mm in length and ≥25 mm in diameter, and the aneurysm involves the common iliac artery and its branches, which are ≥12 mm in diameter. Type D: The AAA involves the internal iliac arteries bilaterally. Type E: AAA proximal aneurysm neck length ≥10 mm, diameter ≥25 mm, or superior mesenteric artery stenosis or occlusion. Schumacher’s classification Type I: proximal neck 1.5 cm, distal neck 1.0 cm. Type IIA: proximal neck 1.5 cm, AAA involving aortic bifurcation. Type IIB: proximal tumor neck 1.5 cm, AAA involving the common iliac artery. Type IIC: proximal tumor neck 1.5 cm, AAA involving iliac artery bifurcation. Type III: proximal tumor neck 1.5 cm. Ahn staging Type I: proximal tumor neck 1.5 cm, distal tumor neck 1.0 cm. Type IIA: proximal tumor neck 1.5 cm, distal tumor neck 25 px AAA involving aortic bifurcation. Type IIB: proximal tumor neck 1.5 cm, AAA involving the common iliac artery. Type III: proximal aneurysm neck 1.5 cm, distal aneurysm neck 1.0 cm Type IV: proximal aneurysm neck 1.5 cm, distal aneurysm neck 1.0 cm AAA involving the aortic bifurcation. Abdominal aortic aneurysms are graded according to the degree of distortion of the AAA neck. Grade I: AAA proximal neck with 180° of distortion. Grade I: AAA proximal neck angulation 150°~180°. Grade II: AAA proximal aneurysm neck angulation 120°~150°. Grade III: AAA proximal tumor neck angulation 120°.