Dilated Aorta
Gregory Kicska, MD, PhD
DIFFERENTIAL DIAGNOSIS
Common
Atherosclerotic
Degenerative
Aortic Stenosis
Less Common
Aortic Dissection
Pseudoaneurysm
Mycotic Aneurysm
Penetrating Atherosclerotic Ulcer
Post-Traumatic Pseudoaneurysm
Rare but Important
Collagen Vascular Diseases
Connective Tissue Disease
Syphilis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Pathology indicated by outer diameter measurements
Measurements providing high specificity for pathology
Ascending > 4.5 cm
Proximal descending > 3.2 cm
Ascending:descending ratio > 1.5:1
Isthmus:hiatus ratio > 1.4:1
Aorta should taper throughout course; focal distal diameter increase of > 50% is abnormal
Morphology
Saccular (false aneurysm): Dissection, mycotic, post-traumatic, penetrating atherosclerotic ulcer (PAU)
Fusiform (true aneurysm): Atherosclerosis, valvular disease
Location
Ascending aorta: Valvular pathology, dissection, connective tissue disease, syphilis
Descending aorta: Dissection, PAU, atherosclerotic, mycotic, post-traumatic
Distance of aneurysm from major branch vessels determines feasibility of stent placement
Tortuosity, calcification, and minimum luminal diameter of iliac arteries determine vascular access strategy
Diameter of proximal and distal aneurysm determines selection of stent size
Etiology of aneurysm (mycotic, inflammatory, or atherosclerotic) influences decision to treat surgically or endovascular
Helpful Clues for Common Diagnoses
Atherosclerotic
Descending aorta: Tortuous, diffuse intimal calcifications, mural thrombus, focal dilation
Caused by intimal disease with fibrous replacement of underlying media
Coexistent small and medium vessel atherosclerosis
Degenerative
Systemic hypertension: Leads to accelerated elastic fiber fragmentation and smooth muscle degeneration
Ascending aortic dilation with relative preservation of root diameter
Older patients
Aortic Stenosis
Dense calcifications of aortic valve
Grade of stenosis related to valve area
> 2.0 cm2: No hemodynamically significant stenosis
2-1.5 cm2: Mild stenosis
1.5-1 cm2: Moderate stenosis
< 1 cm2: Severe stenosis
Aortic bicuspid-related stenosis
Young patient with calcified valve despite paucity of vascular calcifications elsewhere
Prevalence of 1:1,000: Men more commonly affected
Associated with aortic coarctation and patent ductus arteriosus
Prone to dissection
Helpful Clues for Less Common Diagnoses
Aortic Dissection
Intimal calcifications displaced toward aortic lumen: Can be appreciated on unenhanced study
False lumen expands, leading to aortic dilation
Majority of patients present with systemic hypertension
Intimal flap seen on enhanced CT, 3D MRA, or MR black-blood sequence
May occur in areas of prior intramural hematoma or penetrating atherosclerotic ulcer
Pseudoaneurysm
Mycotic Aneurysm
Saccular configuration, irregular lumen, larger than PAU
Adjacent abscess or inflammation
More common etiology in young patients with thoracic aortic aneurysms
Most commonly caused by bacterial infection (Staphylococcus and Salmonella) at site of prior aortic defect
Patients will have prior history of sepsis, IV drug use, endocarditis
Penetrating Atherosclerotic Ulcer
Diffuse atherosclerotic disease present
Penetration of contrast beyond expected outer aortic wall contour
Adjacent inflammatory stranding and wall thickening present
On MR, slow-flowing blood may make PAU appear thrombosed; phase contrast or MRA will more accurately characterize
New PAU found with adjacent inflammation may indicate cause of symptoms in patients presenting with chest pain
Post-Traumatic Pseudoaneurysm
History of high-energy blunt trauma
Aortic contour abnormality at ligamentum arteriosum
Can less commonly occur at aortic root or hiatus
Calcifications indicate remote trauma
Helpful Clues for Rare Diagnoses
Collagen Vascular Diseases
Takayasu/giant cell arteritis
Radiographically indistinguishable; Takayasu suspected in age < 40 years, giant cell suspected in age > 40 years
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
