Aortic dissection occurs when a tear in the intimal layer of the aortic wall allows blood to enter the media, creating a true and false lumen. It is classified by the Stanford system as Type A (involving the ascending aorta) and Type B (confined to the descending aorta). Hypertension is the most important risk factor, and emergent surgical or endovascular intervention may be required. Mortality rate increases by 1-2% per hour if untreated. The DeBakey classification is also used: Type I (entire aorta), Type II (ascending only), Type III (descending only).
Age Range
40-80
Peak Age
60
Gender
Male predominant
Prevalence
Uncommon
In aortic dissection, a tear in the intimal layer allows high-pressure arterial blood to enter the media, creating an intimal flap that separates the true and false lumens. The false lumen is typically larger than the true lumen because the dissecting blood expands under pressure within the media. On CT angiography, the intimal flap appears as a hypodense linear structure between the two lumens; the true lumen enhances earlier in the arterial phase while the false lumen shows delayed enhancement. Within the false lumen, the cobweb sign (fine fibrous strands) and beak sign (acute-angled entry into the lumen) may be seen. Complications include branch vessel obstruction (malperfusion), aortic regurgitation, pericardial tamponade, and rupture.
A thin hypodense linear structure separating two lumens within the aortic lumen on CT angiography — pathognomonic finding of aortic dissection.
A thin, hypodense linear structure within the aortic lumen separating two lumens (intimal flap). The true lumen is typically smaller and enhances more intensely, while the false lumen is larger and shows delayed enhancement.
Report Sentence
An intimal flap is identified within the aortic lumen with formation of true and false lumens.
Fine fibrous strands within the false lumen (cobweb sign). These strands represent incomplete media tears and aid in false lumen identification.
Report Sentence
Cobweb sign (fine fibrous strands) is identified within the false lumen, supporting false lumen identification.
An acute-angled, beak-shaped structure at the origin of the false lumen (beak sign). This finding is considered pathognomonic for false lumen identification.
Report Sentence
Beak sign is identified at the false lumen entry, supporting the diagnosis of dissection.
Delayed enhancement of the false lumen. Due to slower flow within the false lumen, it appears low density in the arterial phase but fills with contrast in the delayed phase. In a thrombosed false lumen, no contrast filling occurs.
Report Sentence
Delayed enhancement of the false lumen is demonstrated on the delayed phase.
Displacement of intimal calcifications inward from the inner surface of the aortic wall on non-contrast CT. This finding indicates separation of the intima from the media layer.
Report Sentence
Displaced intimal calcifications are noted on non-contrast CT, suggestive of aortic dissection.
On MR angiography or dark-blood sequences (T1 dark-blood), the intimal flap appears as a low-signal linear structure. If thrombus is present in the false lumen, hyperintense signal may be seen on T1.
Report Sentence
An intimal flap is identified within the aortic lumen on MRI, consistent with aortic dissection.
Mobile intimal flap within the aortic lumen on transthoracic or transesophageal echocardiography. Doppler demonstrates different flow patterns in the true and false lumens.
Report Sentence
A mobile intimal flap is identified within the aortic lumen on echocardiography, consistent with aortic dissection.
Extension of dissection into branch vessels (carotid, subclavian, celiac, SMA, renal arteries). Branch vessel malperfusion may lead to organ ischemia. Static or dynamic obstruction mechanisms are described.
Report Sentence
Extension of dissection into branch vessels is noted, requiring evaluation for malperfusion.
Criteria
Dissection involving the ascending aorta (DeBakey Type I and II). Entry tear may be in the ascending aorta or arch.
Distinct Features
Emergency surgical indication. Risk of aortic regurgitation, coronary malperfusion, pericardial tamponade. Mortality reaches 50% if untreated.
Criteria
Dissection confined to the descending aorta (DeBakey Type III). Entry tear distal to the left subclavian artery.
Distinct Features
Generally medical management (blood pressure control). Complicated Type B (malperfusion, rapid expansion, rupture risk) requires endovascular treatment (TEVAR).
Criteria
Hematoma within the aortic wall without classic intimal flap or false lumen flow. Considered a variant of dissection.
Distinct Features
Crescent-shaped hyperdense wall thickening on non-contrast CT. Absence of intimal flap distinguishes from classic dissection. 10-30% of cases progress to classic dissection.
Criteria
Dissection present for more than 14 days. The intimal flap has become thickened and immobile.
Distinct Features
False lumen may be thrombosed or organized. Intimal flap thickened, may calcify. Aneurysmal dilatation may develop. Annual follow-up required.
Distinguishing Feature
Intramural hematoma has NO intimal flap or false lumen flow; crescent-shaped hyperdense wall thickening on non-contrast CT.
Distinguishing Feature
Penetrating aortic ulcer shows focal contrast outpouching; there is no extensive dissection flap. Usually associated with advanced age and severe atherosclerosis.
Distinguishing Feature
Aortic rupture shows active contrast extravasation, retroperitoneal/mediastinal hematoma, and draped aorta sign. Unlike dissection, intimal flap is not typical.
Distinguishing Feature
Aortic aneurysm has lumen dilatation without intimal flap. Mural thrombus may be present but there is no true and false lumen separation.
Distinguishing Feature
Takayasu arteritis shows long-segment concentric wall thickening and enhancement; no dissection flap. Occurs in young women.
Urgency
emergencyManagement
surgical/endovascularBiopsy
Not NeededFollow-up
lifelong imaging surveillanceStanford Type A dissection is an emergency surgical indication (ascending aorta replacement). Uncomplicated Type B is managed with medical therapy (beta-blockers, blood pressure control). Complicated Type B (malperfusion, rupture, rapid expansion) requires TEVAR. Lifelong imaging surveillance (CT angiography) is mandatory.
Stanford A dissection (ascending aorta) is an emergency surgical indication — untreated mortality increases 1-2%/hour within hours. Stanford B dissection is managed medically (antihypertensives); complicated cases require TEVAR. Malperfusion syndromes (renal, mesenteric, limb) require urgent intervention.