statdx/docs_md/articles/dilatation-of-thoracic-aorta_3b177a9c-04f3-4d15-9d18-decc5c236e7e.md

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title: "Dilatation of Thoracic Aorta" docid: "3b177a9c-04f3-4d15-9d18-decc5c236e7e" authors:

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ESSENTIAL INFORMATION

• Key Differential Diagnosis Issues

  • Ascending aorta dilated ≥ 4.0 cm, aneurysmal ≥ 5.0 cm
  • Descending thoracic aorta aneurysmal ≥ 4.0 cm

• Helpful Clues for Common Diagnoses

  • Atherosclerotic Aneurysm - Fusiform aortic aneurysms most common - Typically arise from ascending aorta - Dilation of aorta typically in presence of significant atherosclerotic disease - Commonly contain thrombus - Saccular aneurysms have increased risk of rupture
  • Penetrating Atherosclerotic Ulcer - Focal contrast-filled outpouching of aortic wall; underlying atherosclerotic disease - More common in descending aorta or aortic arch - Associated with intramural hematoma, aortic dissection - Vast majority of patients have underlying hypertension and history of smoking

• Helpful Clues for Less Common Diagnoses

  • Ductus Diverticulum - Focal outpouching along anterior wall at aortic isthmus - Smooth angles, obtuse shoulders - Sagittal images may show diverticulum contiguous with ligamentum arteriosum - May contain thrombus and wall calcification
  • Traumatic Pseudoaneurysm - Most common location is aortic isthmus (may also be seen at aortic root or diaphragmatic hiatus) - Focal contrast-filled outpouching along undersurface of aortic arch/anterior wall of aortic isthmus - Unlike ductus diverticulum, traumatic pseudoaneurysms have sharp angles, irregular margins, and possible visible intimal flap - Associated mediastinal hematoma may be present
  • Postoperative Pseudoaneurysm - Contrast-filled outpouching beyond walls of aorta associated with surgical changes - Commonly seen with aortic valve replacement (especially in cases of endocarditis) and graft repair - Noncontrast imaging useful to detect high-attenuation surgical material mimicking pseudoaneurysm

• Helpful Clues for Rare Diagnoses

  • Aortitis - Most commonly involve thoracic aorta: Takayasu and giant cell arteritis - Leads to wall thickening, irregular aortic contours, aneurysm formation, and narrowing/occlusion - Aneurysm may be fusiform or saccular - Calcification may be present in chronic cases - MR findings - Thickened walls with high signal intensity on T2WI - Enhancement of arterial wall - Mycotic aortitis may cause dilation - Hematogenous spread of organisms (Staphylococcus aureus and Salmonella species most common)

References

Selected References

1. Saremi F et al: Image predictors of treatment outcome after thoracic aortic dissection repair. Radiographics. 38(7):1949-72, 2018

Images

Selected Images

Atherosclerotic Aneurysm PA chest radiograph shows dilation of the thoracic aorta, evidenced by abnormal contour of the aortic arch and displacement of the intrathoracic trachea to the right . The ascending aorta is visible overlying the right hilum.

Atherosclerotic Aneurysm PA chest radiograph shows dilation of the thoracic aorta, evidenced by abnormal contour of the aortic arch and displacement of the intrathoracic trachea to the right . The ascending aorta is visible overlying the right hilum.

Atherosclerotic Aneurysm Axial CECT of the same patient shows aneurysm of the descending thoracic aorta and calcified and noncalcified atherosclerotic disease of the aorta. Atherosclerosis is the most common cause of aortic dilation.

Traumatic Pseudoaneurysm Double oblique MRA of the thoracic aorta in a patient with a history of thoracic trauma shows a saccular aneurysm of the aortic arch. Acute angles of the aneurysm differentiate this pseudoaneurysm from a ductus diverticulum.

Traumatic Pseudoaneurysm Composite image with axial CECT (left) and NECT (right) shows focal dilation of the ascending aorta with high attenuation in the expected location of the medial aortic wall representing postsurgical material rather than aortic pathology.

Postoperative Pseudoaneurysm PA chest radiograph of a patient with a history of bicuspid aortic valve and coarctation status post stent placement in the proximal descending thoracic aorta shows new dilation of the aortic arch and descending aorta . The intrathoracic trachea is displaced to the right .

Postoperative Pseudoaneurysm Coronal reformatted CECT of the same patient shows the descending thoracic aortic stent complicated by large, complex contrast outpouchings , consistent with postoperative pseudoaneurysms.

Aortitis Axial CECT of a patient with sepsis and chest pain shows aneurysmal dilation of the proximal descending thoracic aorta with associated diffuse aortic wall thickening and enhancement , consistent with infectious aortitis.

Aortitis Fused coronal reformatted FDG PET/CT of the same patient shows diffuse FDG avidity of the thickened, aneurysmal descending thoracic aorta . A large left pleural effusion is also present. Staphylococcus and salmonella are frequent organisms causing infectious aortitis.