Archived case 180 · July 22-July 29, 2015
27-year-old man involved in a high-speed motor vehicle collision. The trauma bay chest radiograph raised the question of hemomediastinum and possible acute aortic injury.
What are the pertinent imaging findings? Is there CT evidence of a post-traumatic aortic injury? What if anything should be done next?
Radiologic Findings Contrast-enhanced sagittal oblique multi-planar reconstruction (MPR) CT Angiogram (mediastinal window) demonstrates a focal convex bulge in the aortic isthmus. Notice the shorter, steeper slope superiorly and the gentler appearing slope inferiorly. The margins appear smooth and uninterrupted. No mediastinal hemorrhage is present. Answer Diagnosis: Atypical ductus diverticulum (no injury; no further investigation needed)
Atypical ductus diverticulum (no injury; no further investigation needed)
Answer
Diagnosis: Atypical ductus diverticulum (no injury; no further investigation needed)
Differential Diagnosis
None
Discussion
• MDCT is now the definitive test for both diagnosing and excluding potential acute traumatic aortic injury (ATAI) and great vessel injury (GVI) without the need for transcatheter aortography (TCA) or transesophageal echosonography (TEE)
• TCA and TEE are now reserved for the infrequent setting of equivocal MDCT results
• The increased use MDCT of in trauma patients has led to the recognition of vascular variants such as the ductus diverticulum, atypical ductus diverticulum, and the aortic spindle which may mimic an acute injury
• The CT signs of potential ATAI are broadly classified as Direct and Indirect
• Direct CT Signs of Vascular Injury include:
· Pseudoaneurysm
· Intimal flap-dissection
· Focal contour abnormality
· Abrupt aorta or branch vessel caliber change
· Intraluminal thrombosis or debris
· Contrast extravasation
· Indirect CT Signs of Potential Vascular Injury include
· Subtle contour abnormalities
· Hemomediastinum
· Peribranch vessel hematoma
· Para-aortic blood
None of these signs are present in the test case.
The Ductus diverticulum is either a remnant of the ductus arteriosum or the right dorsal aortic root. The most common diagnostic challenge for radiologists on trauma chest CTA’s is the 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 4 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
An Atypical ductus diverticulum (test case)- often causes even more diagnostic confusion; characterized superiorly by a shorter, steeper slope and inferiorly by a more typical, gentler slope
PEARLS: Most aortic injuries are associated with mediastinal hemorrhage. Subtle injuries may occur with little or no hemomediastinum. Hemomediastinum is most often related to bleeding from small veins and arteries, or cervico-thoracic spinal or sternal fractures and not from the aorta itself.
Selected Readings
1. Goodman PC, Jeffrey RB, Minagi H, Federle MP, Thomas AN. The Angiographic Evaluation of the Ductus Diverticulum. Cardiovasc Intervent Radiol 1982; 5:1-4.
2. Grollman JH. The Aortic Diverticulum: A Remnant of the Partially Involuted Dorsal Aortic Root. Cardiovasc Intervent Radiol 1989; 12:14-17.
3. Macura KJ, Corl FM, Fishman EK, Bluemke DA. Pictorial Essay: Pathogenesis in Acute Aortic Syndromes: Aortic Aneurysm Leak and Rupture and Traumatic Aortic Transection. AJR Am J Roentgenol 2003; 181: 303-307.
4. Parker MS, Rosado de-Christenson ML, Abbott GF. Thoracic Trauma: Anatomic Variants Simulating Acute Aortic Injury. In: Chest Imaging Case Atlas, Thieme New York 2012; 491-494.Original case written by its authors at Virginia Commonwealth University and published at this address as part of a weekly teaching collection. Reproduced here as an archive.