This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'On barium swallow which of the following will cause posterior impression - \nSelect and explain. \nA. Left atrium, B. Aortic knuckle, C. Pulmonary sling, D. Aberrant right subclavian artery', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Aberrant right subclavian artery arises from aortic arch just distal to the left subclavian artery. It travels behind the esophagus and after crossing the esophagus (from left to right) it courses as the right subclavian artery. Aberrant right subclavian artery produces the classical appearance of a posterior impression on the proximal esophagus and left sided aortic arch impression (as it arises from left side of aortic arch) on barium swallow.\nPlain Radiograph with barium swallow\n\nAberrant right subclavian artery\xa0:-\xa0\xa0\xa0\n\ti) Left sided aortic arch impression\xa0\n\tii) Posterior impression on esophagus\nAberrant left subclavian artery\xa0:-\xa0\xa0\xa0\xa0\xa0\n\ti) Right sided aortic arch impression\n\tii)\xa0Posterior impression on esophagus\n\tiii)\xa0Anterior displacement of esophagus\n\tiv)\xa0Compression of trachea', 'role': 'assistant'}]