Barium Swallow and Computed Tomography Angiographic Diagnosis of Descending Thoracic Aortic Diverticulum in Right-sided Aortic Arch: Rare Cause of Dysphagia

Abstract

Descending thoracic aortic diverticulum associated with right-sided aortic arch is a very rare etiology of dysphagia. This report presents the case of a 42-year-old male who came with worsening dysphagia to solids, where barium swallow revealed smooth posterior esophageal indentation, and computed tomography (CT) angiography demonstrated Edwards Type I mirror-image branching with a descending aortic diverticulum indenting the esophagus. This case served to emphasise the value of vascular anomalies being considered as a reason for unexplained dysphagia. Barium swallow and CT angiography gave complementary functional and anatomic assessment, facilitating accurate diagnosis and management planning of unusual aortic diverticula.

INTRODUCTION

A diverticulum is a congenital outpouching from the wall of a hollow or tubular structure.[1] Congenital aortic arch malformations are uncommon (<1% of the population), and right-sided aortic arch (RAA) is only found in approximate 0.05%–0.1% of the population.[2] Edwards categorized RAA into three forms: Type I – mirror-image branching; Type II – anomalous left subclavian artery with Kommerell’s diverticulum (KD); and Type III– solitary subclavian artery from the pulmonary artery through the ductus arteriosus. Even though Type I is typically not associated with symptoms, related anomalies like diverticula may cause occasional symptoms such as dysphagia. Computed tomography (CT) angiography is of particular value in detecting these vascular variations.[3]

Aortic arch anomalies can be asymptomatic or symptomatic from compressive effects on account of their close relationship with the trachea and esophagus. If a diverticulum or anomalous vessel compresses the esophagus, dysphagia – dysphagia lusoria – may ensue.[4] Kommerell’s diverticulum, being a persistence of the dorsal aortic arch, is of special interest because its aneurysmal dilation may cause such symptoms.[5] Most cases of RAA with KD reported in the literature involve dissection or aneurysm more than dysphagia as the initial presentation. Esophageal compression occurs due to a retro-esophageal diverticulum from a right-sided descending aorta.

The following is a very rare case of a descending thoracic aortic diverticulum related to Type I RAA, with a presentation of dysphagia. It illustrates the value of barium swallow and CT angiography in diagnosis and adds to the limited number of cases of the radiologic spectrum of RAA anomalies.

CASE REPORT

A 42-year-old man had progressive dysphagia to solids for the previous 7 months. No history of weight loss, trauma, previous thoracic operation, or infection. Physical examination was unrevealing. To assess the etiology of dysphagia, a barium swallow study and contrast-enhanced CT angiography were done.

The barium swallow showed a smooth posterior indentation of the mid-thoracic esophagus with mild proximal dilatation, with no intrinsically evident mucosal abnormality, stricture, or mass lesion [Figure 1]. This was followed by CT angiography with 1-mm collimation to evaluate the vascular anatomy and its relationship to the esophagus. The CT showed a right aortic arch with Edwards Type I mirror-image branching pattern, which included the left brachiocephalic trunk (further dividing to the left common carotid and left subclavian arteries), then the right common carotid and right subclavian arteries [Figure 2].

Figure 1.

Barium Swallow (right oblique view) showing posterior indentation of the mid-thoracic esophagus (arrow)

Figure 2.

Computed tomography (CT) angiography (1-mm collimation) with coronal and sagittal reformatted images, (a) Axial CT shows ascending aorta and descending aorta (DA), DA is seen to the right of trachea, (b) Descending aorta is seen posteriorly and right lateral to trachea, (c) Left brachiocephalic trunk (left BCT) is seen arising as 1^st branch of aortic arch, (d) (diverticulum) is seen arising at the same level from the left lateral wall of descending aorta, (e) left common carotid artery (left CCA) and left subclavian artery (left SA) are seen as branches of left BCT, (f) Slight tracheal deviation towards left is seen, (g) right CCA and right SA are seen arising as 2^nd and 3^rd branches of aortic arch, (h) Coronal CT shows D (diverticulum) causing compression over esophagus, (i) Sagittal CT shows D (diverticulum) indenting posterior margins of esophagus. AA = Ascending Aorta, DA = Descending aorta, BCT = Brachiocephalic trunk, D = Diverticulum, LCCA = Left common carotid artery, LSA = Left subclavian artery, RCCA = Right common carotid artery, RSA = Right subclavian artery

A diverticulum was noted from the left lateral wall of the descending thoracic aorta, about 3 cm below the origin of the right subclavian artery. The diverticulum was 16.2 cm × 12 cm × 16 mm in size, with a neck of 14 mm and a dome depth of 4.6 mm. The diverticulum produced lateral displacement as well as moderate compression of the esophagus, whereas the rest of the thoracic aorta was normal with no calcification, mural thrombus, dissection, or aneurysmal dilatation. Coronal and sagittal reformatted images further clarified the spatial relationship of the diverticulum with the trachea and esophagus and established the vascular indentation as the probable etiology for the patient’s dysphagia.

DISCUSSION

The aortic arch and its major branches form during embryologic development through a complex process involving the six paired pharyngeal (aortic) arches and dorsal aortae. Normally, the left fourth aortic arch and left dorsal aorta persist and give rise to the definitive aortic arch and descending aorta, while the right fourth arch regresses. When this pattern is altered – specifically when the right fourth arch persists, and the left regresses – a RAA is formed.[5,6]

In the classification proposed by Edward H. D. Archer Edwards, RAA is subdivided into: Type I (mirror‐image branching), Type II (aberrant left subclavian artery often with a diverticulum of KD), and Type III (isolation of the left subclavian artery). In Type I, the first branch is the left brachiocephalic trunk (further divides into left common carotid and left subclavian arteries), followed by right common carotid and right subclavian arteries.[7]

In this case, we saw an RAA Type I with mirror‐image branching – not normally symptomatic in the majority of people. Our patient, however, presented with progressive dysphagia, which prompted further imaging that revealed a diverticulum of the descending thoracic aorta arising from the left lateral wall, displacing and compressing the esophagus. Whereas esophageal compression due to vascular malformations is fully characterized in aberrant subclavian arteries and Kommerell diverticula of RAA, the presence of a descending aortic diverticulum that forms independently of branch vessels in Type I RAA is vanishingly rare.

The barium swallow study clearly showed a smooth posterior indentation of the mid-thoracic esophagus with proximal dilatation – suggesting extrinsic compression and not intrinsic esophageal disease. This was then followed by high‐resolution contrast-enhanced CT angiography with multiplanar and three-dimensional reconstructions, which accurately defined the arch branching pattern, the morphology of the diverticulum (neck diameter, dome depth), and the relationship with mediastinal structures such as the esophagus. Stepwise imaging highlights the utility of integrating functional (barium swallow) and anatomical (CT angiography) studies in suspected vascular etiology of dysphagia.[8]

Its management continues to be difficult because of its infrequency and absence of guideline-directed recommendations. In published series, indications for intervention are usually symptoms (e.g., compression, dysphagia, airway obstruction), large diverticulum size, aneurysmal transformation, or dissection evidence.[9,10] With symptomatic presentation (dysphagia) and obvious anatomical substrate, referral to a cardiothoracic surgical team for multidisciplinary evaluation was made. A conservative “watchful waiting” policy could be considered in asymptomatic, stable cases with imaging follow-up – but symptomatology in our case shifted the balance of inquiry toward active evaluation for intervention.

CONCLUSION

Descending thoracic aortic diverticulum in the context of RAA is a rare vascular anomaly that may present exceptionally with dysphagia. Diagnosis of the condition needs a high index of suspicion, especially when investigations for dysphagia by standard workup are not helpful. Barium swallow and CT angiography yield complementary information on both functional and anatomical domains, helping with accurate diagnosis. Knowledge of such vascular etiologies can prevent undue delays in appropriate management by clinicians.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.