Figure 52-14 The Crawford classification of thoracoabdominal aortic aneurysms is defined by anatomic location and the extent of involvement. Type I aneurysms involve all or most of the descending thoracic aorta and the upper abdominal aorta; type II aneurysms involve all or most of the descending thoracic aorta and all or most of the abdominal aorta; type III aneurysms involve the lower portion of the descending thoracic aorta and most of the abdominal aorta; and type IV aneurysms involve all or most of the abdominal aorta, including the visceral segment. (Adapted from Crawford ES: Thoracoabdominal and suprarenal abdominal aortic aneurysm. In Ernst CB, Stanley JC [eds]: Current Therapy in Vascular Surgery. Philadelphia, Decker, 1987, pp 96–98.)