Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP view of the chest demonstrates low lung volumes , which accentuate bronchovascular markings . Retrocardiac opacity is noted . There is no pleural effusion or pneumothorax . The descending aorta appears tortuous . The hilar and mediastinal silhouettes are unremarkable . The heart size is top normal . There is no pulmonary edema .
    OUTPUT:
    
Retrocardiac opacity may represent atelectasis or infection in the appropriate clinical setting .