|Year : 2015 | Volume
| Issue : 2 | Page : 250-253
Imaging findings in the right aortic arch with mirror image branching of arch vessels: An unusual cause of dysphagia
Guneet Singh, Amit Kharat, Preeti Sehrawat, Vilas Kulkarni
Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D Y Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||13-Mar-2015|
3-B, Khalsa College Colony, Patiala - 147 001, Punjab
Source of Support: None, Conflict of Interest: None
We report a case of a 72-year-old female with a right aortic arch with mirror-image branching of arch vessels presenting with dysphagia, and characteristic images on barium esophagogram, contrast-enhanced computed tomography scan, and magnetic resonance aortography. Right-sided thoracic aortic arch with mirror-image branching of the brachiocephalic vessels causing dysphagia without associated congenital cardiac anomalies is extremely uncommon. Right-sided aortic arch is a rare congenital abnormality with incidence of 0.05-0.1% in the normal population. Anomalies of great vessels are usually incidental findings, because they are asymptomatic. Right aortic arch infrequently presents with a vascular ring that can cause complete or partial obstruction of the trachea and/or esophagus. The understanding of this arch anomaly is based on Edward's hypothesis about the double arch system during embryonic developmental.
Keywords: Barium swallow, contrast-enhanced computed tomography scan and magnetic resonance aortography, right aortic arch, symptomatic
|How to cite this article:|
Singh G, Kharat A, Sehrawat P, Kulkarni V. Imaging findings in the right aortic arch with mirror image branching of arch vessels: An unusual cause of dysphagia. Med J DY Patil Univ 2015;8:250-3
| Introduction|| |
Right-sided aortic arch is a rare congenital abnormality with incidence of 0.05-0.1% in the normal population. , Imaging of vascular rings in the superior mediastinum can be challenging. Previously, these used to be confirmed by indirect signs like "vascular impression created on the barium filled esophagus" or invasive tests like conventional angiography. However, with the advent of high-resolution cross-sectional imaging modalities like computed tomography (CT) and magnetic resonance imaging, these vascular rings and differentials such as aberrant vessels, aortic diverticulum, and associated cardiac anomalies can be imaged in a noninvasive manner.
| Case Report|| |
A 72-year-old female presented with a history of gradually progressive dysphagia. Chest radiograph revealed right hilar prominence. Differential of hilar lymphadenopathy/ascending aortic arch aneurysm/right-sided aortic arch was considered [[Figure 1] frontal chest radiograph]. On further evaluation by barium swallow demonstrated a posterior impression on esophagus on the lateral view and right-sided impression on frontal view of the esophagogram consistent with findings of vascular ring [[Figure 2]a frontal view and 2b lateral view]. Echocardiography revealed normal intracardiac anatomy, mild pulmonary arterial hypertension, and right-sided aortic arch. CT with intravenous contrast revealed a right aortic arch with retro-esophageal position displacing trachea and esophagus anterolaterally toward the left side. Lower axial sections demonstrated that the aortic arch descended in the right side of the thorax [[Figure 3]a-e axial images cranio-caudal direction]. Magnetic resonance aortography revealed a right aortic arch with mirror-image branching of great arteries arising from the arch [Figure 4]a and b.
|Figure 2: (a) frontal view and (b) lateral view of barium swallow demonstrating a right-sided impression (arrow) and a posterior impression (arrow) on esophagus on frontal view and lateral view esophagogram, respectively|
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|Figure 3: (a-e) (axial images cranio-caudal direction) computed tomography with intravenous contrast showing a right aortic arch (thick arrow) with retro-esophageal position displacing trachea (asterisks) and esophagus (thin arrow) anterolaterally toward the left side. Lower axial sections demonstrated that the aortic arch descended in the right side of the thorax|
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|Figure 4: (a and b) maximum intensity projection images showing a right aortic arch with mirror-image branching of great arteries arising from arch and (b) left innominate artery (arrow)|
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| Discussion|| |
In normal embryonic morphogenesis, development of the aorta and its branches starts between the 4 th and 7 th weeks of gestation from five pairs of pharyngeal arch arteries in a symmetrical manner. Evolution of the aortic arch and its branches occurs as a result of asymmetric involution and persistence of specific embryologic arch structures. ,, Congenital malformations of the aortic arch arise from disorders in the formation of the primitive double aortic arch.  Anomalies of great vessels are incidental findings as they are usually asymptomatic. , Right aortic arch with mirror-image branching of great arteries (Edwards Type I) is rare congenital abnormality with incidence of 0.05-0.1% in the normal population and 75-85% of the cases are usually associated with cyanotic congenital heart disease such as tetralogy of Fallot and truncus arteriosus. ,, Right aortic arch occasionally forms a vascular ring which can cause complete or partial obstruction of the trachea and/or esophagus and present with any of the following symptoms such as dysphagia, dyspnea, stridor, wheezing, cough, recurrent respiratory tract infections, chest pain, or respiratory distress. 
The understanding of this anomaly is based on Edward's hypothesis about the double arch system during embryonic developmental. In the evolving double aortic arch, the normal left aortic arch develops when there is complete regression of the portion of the right arch between the right subclavian artery and the descending aorta [Figure 5]. Similarly, when regression occurs in the same region in the contralateral left arch, right aortic arch with mirror-image branching develops. In almost all cases, the regression occurs between the left ductus and the descending aorta, resulting in mirror-image branching without a complete vascular ring (Edwards Type I) [Pie Chart 1 [Additional file 1] and [Figure 6]]. In very rare cases, the regression occurs between the left subclavian artery and the left ductus. In this situation, the left ductus extends from the diverticulum of the descending aorta to the left pulmonary artery and thereby completing a potentially symptomatic vascular ring [Figure 7]. The ductus cannot be imaged directly, therefore, the imaging appearance of this arch anomaly will be the similar to Edwards Type I right aortic arch except for a left sided retro-esophageal aortic diverticulum and posterior impression of the vascular ring on lateral esophagogram. ,
|Figure 5: Normal left arch develops after complete regression of the distal portion of the right arch in embryologic double aortic arch (shaded segment). R: Right, L: Left, CCA: Common carotid artery, SA: Subclavian artery, PA: Pulmonary artery, Ao: Aorta, Tr: Trachea, Os: Oesophagus (modifi ed from Shuford, et al.)|
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|Figure 6: Right aortic arch with mirror-image branching (Edward Type I without vascular ring or aortic diverticulum) occurs when complete involution (shaded segment) is present in the left aortic arch distal to left ductus. R: Right, L: Left, CCA: Common carotid artery, SA: Subclavian artery, PA: Pulmonary artery, Ao: Aorta, Tr: Trachea, Os: Oesophagus (modifi ed from Shuford, et al.)|
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|Figure 7: Right aortic arch with mirror-image branching with vascular ring and aortic diverticulum, occurs when complete involution (shaded segment) is present in left aortic arch between left subclavian artery and ductus. R: Right, L: Left, CCA: Common carotid artery, SA: Subclavian artery, PA: Pulmonary artery, Ao: Aorta, Tr: Trachea, Os: Oesophagus (modifi ed from Shuford, et al.)|
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In the present case, the right aortic arch persisted during embryonic development as a result of regression of the left arch between the left subclavian artery and the left ductus arteriosus thus, forming a potential vascular ring causing symptom of dysphagia. On imaging, lateral esophagogram showed a posterior impression on the esophagus.
| Conclusion|| |
In an elderly person presenting with dysphagia, differentials of vascular ring should also be considered as a cause of dysphagia. Radiologist should be alert in assessing cross-sectional imaging to rule out such anomalies which can present later in adulthood.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]