Right aortic arch with aberrant left subclavian artery

Background Right-sided aortic arch (RAA) is a rare congenital abnormality of the aorta, with incidence 0.05%-0.1% on general population. Although they are usually found as incidental findings, sometimes these anomalies can be found as a copycat of mediastinal abnormalities. Imaging plays a major role in the detection of these abnormalities. Objective To dedicate cases of RAA and describe what radiologists need to know. Method A 50-years-old female with lung cancer. From the scout view of enhanced CT of chest, her mediastinum appeared enlarge. Evidently, the enlargement of the mediastinum is caused by right-sided aortic arch. There was also a mass in her right lung. Result Mediasitnum enlargement on the patient was discovered on scout view. Enhanced CT proved that the enlargement is caused by RAA. The patient has RAA with aberrant left subclavian artery (type II based on Edward’s classification), that arising from a diverticulum of Kommerell. CT scan is used to evaluate arch vessels branching and also effect on surrounding organs such as esophagus and trachea. Conclusion RAA is a rare congenital aortic arch anomaly, which can be present as an incidental finding or imitator of mediastinal abnormalities. Understanding of the radiological image of RAA is useful for radiologists to avoid mistake on interpretation. Radiologist’s primary role is to identify these anomalies and to look for compression effect on trachea or esophagus.