101 Anatomic Variants Simulating Acute Injury

Clinical Presentation

46-year-old man involved in a MVC with a clinical concern of hemomediastinum and potential acute traumatic aortic injury

Radiologic Findings

Contrast-enhanced sagittal oblique MIP CT (mediastinal window) (Fig. 101.1) demonstrates a focal convex bulge in the aortic isthmus consistent with a Type III ductus diverticulum. Note the smooth contour and obtuse margin formed with the aortic lumen and the absence of an intimal flap and hemomediastinum.

Diagnosis

Type III Ductus Diverticulum

Differential Diagnosis

None

Discussion

Background

The increased use of MDCT has led to the recognition of numerous vascular variants that may mimic acute aortic injuries. The most common variants include typical ductus diverticulum, atypical ductus diverticulum, aortic spindle, and branch vessel infundibula.

Fig. 101.1

Ductus diverticulum is a remnant of either the ductus arteriosum or the right dorsal aortic root. The most common diagnostic challenge for radiologists on trauma chest CTAs is differentiation of a post-traumatic aortic isthmus pseudoaneurysm from a normal Type III ductus diverticulum. Both aortic entities occur in roughly the same anatomic location, often leading to diagnostic confusion. There are four distinct variations in the contour of the aortic isthmus as follows:

Type I— concave contour

Type II— mild straightening or convexity without a discrete bulge

Type III—discrete focal bulge referred to as the ductus diverticulum (Fig. 101.1)

Atypical ductus diverticulum—often causes even more diagnostic confusion; characterized superiorly by a shorter, steeper slope and inferiorly by a more typical, gentler slope (Fig. 101.2)

Aortic spindle

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