2.1. Study patients

This retrospective study in a single institution was conducted with approval from the ethics review board of the Nippon Medical School. At our institution, 51,057 abdominal CE-CT scans were performed between January 2005 and December 2016 excluding subsequent abdominal CE-CT scans of the same patients. Furthermore, the indication for 3237 abdominal CE-CT scans was for abdominal symptoms. A Picture Archiving and Communication Systems (PACS) database search for key words (arterial dissection, dissecting aneurysm) in the reports was performed using to extract SIVAD patients. Patients with concomitant aortic dissection, trauma, or iatrogenic causes were excluded [[3], [4], [5], [6],15,16].