 Aortic dissections are the results of a disruption in the aortic wall with blood flow into the media resulting in a true and false lumen, which may propagate antegrade or retrograde. Aortic dissections are classified by acuity, anatomic location of entry tear, extent of false lumen, and presence or absence of complicating features. The Stanford classification is commonly used to categorize aortic dissections. Type A dissection involves the ascending aorta (and may extend distally), and type B dissection is limited to the aortic arch and descending thoracic aorta. Complicating features include cerebral, coronary, and/or visceral malperfusion syndrome as well as rupture. Aortic dissections may require emergent surgical repair, thoracic endovascular aortic repair (EVAR), or other endovascular interventions to treat malperfusion syndromes following initial medical therapies. Aneurysmal expansion of the false lumen occurs in up to 50% of patients requiring follow-up imaging. Traditionally, treatment for thoracoabdominal aneurysm or dissection has been surgical. Although surgical repair demonstrated a survival benefit over medical management, open TAAA repair carries high mortality and morbidity risks [3-5]. A 2016 analysis of outcomes of more than 3,000 TAAA repairs reports an operative mortality rate of 7.5%, with permanent paraplegia in 2.9%, permanent renal failure in 5.7%, and stroke in 2.2% for a total composite rate of an adverse event of 14.4% [3]. Over the past 10 to 20 years, alternative treatment regimens have been The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org
Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up.  Aortic dissections are the results of a disruption in the aortic wall with blood flow into the media resulting in a true and false lumen, which may propagate antegrade or retrograde. Aortic dissections are classified by acuity, anatomic location of entry tear, extent of false lumen, and presence or absence of complicating features. The Stanford classification is commonly used to categorize aortic dissections. Type A dissection involves the ascending aorta (and may extend distally), and type B dissection is limited to the aortic arch and descending thoracic aorta. Complicating features include cerebral, coronary, and/or visceral malperfusion syndrome as well as rupture. Aortic dissections may require emergent surgical repair, thoracic endovascular aortic repair (EVAR), or other endovascular interventions to treat malperfusion syndromes following initial medical therapies. Aneurysmal expansion of the false lumen occurs in up to 50% of patients requiring follow-up imaging. Traditionally, treatment for thoracoabdominal aneurysm or dissection has been surgical. Although surgical repair demonstrated a survival benefit over medical management, open TAAA repair carries high mortality and morbidity risks [3-5]. A 2016 analysis of outcomes of more than 3,000 TAAA repairs reports an operative mortality rate of 7.5%, with permanent paraplegia in 2.9%, permanent renal failure in 5.7%, and stroke in 2.2% for a total composite rate of an adverse event of 14.4% [3]. Over the past 10 to 20 years, alternative treatment regimens have been The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org