Figure 13a. Abdominal aortic stenosis due to retroperitoneal fibrosis. (a) Contrast-enhanced axial CT image shows an irregular mass (white arrows) around the abdominal aorta, producing severe aortic narrowing (black arrow). (b, c) Coronal (b) and sagittal (c) reformatted images of the abdominal aorta demonstrate severe aortic stenosis (black arrow) secondary to retroperitoneal fibrosis (white arrows).