Objectives: To investigate the incidence of congenital findings on chest X-ray interpretation. Design: A cross - sectional study.Setting and Participants: The subjects consisted of 152,815 cases who consulted our institute for health screening. Measurement and Results: The incidence of azygos lobe was 0.050% in males and 0.046% in females. The rate of right aortic arch was 0.059% in males and 0.057% in females. The incidence of visceral inversion was 0.014% in males and 0.041% in females. Conclusions: We presented cases with an azygos lobe or right aortic arch, which were occasionally noted on chest X-ray interpretation. Their incidence was almost one in every 2,000 people. However, we should pay attention to them, because they might be misidentified as a pulmonary bulla or mediastinal tumor, respectively.

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