Morphologic Evaluation of Ductus Diverticulum Using Multi - Detector Computed Tomography: Comparison with Traumatic Pseudoaneurysm of the Aortic Isthmus

Abstract

Objectives: To evaluate morphologic variations at the aortic isthmus with particular attention to ductus diverticulum, a mimicker of traumatic pseudoaneurysm, and to describe differences using Computed Tomography (CT) images.

Patients and methods: From December 2013 to December 2014, patients who underwent a chest CT examination after blunt trauma at our emergency department were included. Aortic isthmus morphologies were evaluated using multiplanar reconstruction (MPR) and maximum intensity projection (MIP) images as follows. Type I -concave contour, type II -convexity without a discrete bulge, or type III -a discrete focal bulge (defined as ductus diverticulum).

Results: After excluding 11 cases of traumatic pseudoaneurysm of the aortic isthmus, a total of 432 trauma patients (mean age = 47.1 ± 19.1 years, number of males = 318) were evaluated for aortic isthmus morphology, and classified as follows; type I (n = 240, 55.6%), type II (n = 157, 36.3%), and type III (n = 35, 8.1%). As compared with traumatic pseudoaneurysm (n = 11), ductus diverticulum had a smaller vertical diameter (5.5 ± 1.3 mm vs. 11.2 ± 2.7 mm, P < 0.001), a broader base (14.9 ± 4.1 mm vs. 8.8 ± 4.5 mm, P < 0.001), a smoother margin (97.1% vs. 27.3%, P < 0.001), and formed obtuse angle with the aortic wall. Furthermore, ductus diverticulum was not associated with the presence of a dissection flap or hemomediastinum.

Conclusion: Ductus diverticulum, a mimicker of traumatic pseudoaneurysm of the aortic isthmus, is a frequently observed anatomic variant during CT examinations. Familiarity with its CT imaging findings could avoid it being confused with traumatic pseudoaneurysm in blunt trauma patients.

Keywords: Aorta, Thoracic; Ductus Diverticulum; Tomography, X-ray Computed; Trauma.

Figure 1.. Maximal intensity projection images of three morphologic variants of aortic isthmus; A, Type I, concave contour with parallel walls and uniform diameter; B, Type II, diffuse mild convexity of the aortic isthmus; C, Type III, aortic isthmus demonstrating focal bulge (arrow), which is referred to as ductus diverticulum; Ductus diverticulum has a smooth margin and a broad base and meets the aortic wall at an obtuse angle.

Figure 2.. CT images of acute traumatic pseudoaneurysm of the aortic isthmus; A, Maximal intensity projection image of traumatic pseudoaneurysm of the aortic isthmus; The protrusion meets the aortic wall at an acute caudal angle; B, Axial image shows a dissection flap (arrow) and hemomediastinum.