Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiograph obscuration of the right heart border which on the lateral radiograph corresponds to a linear opacity . This appears to have been present on examination dated ___ , may be post infectious / inflammatory in etiology or atelectasis , slightly more conspicuous . Retrocardiac is slightly more conspicuous relative to prior study , may reflect a small hiatal hernia or confluence of shadows . There is no pleural effusion or pneumothorax . Cardiomediastinal and hilar contours are within normal limits . No evidence of pulmonary edema .
    OUTPUT:
    
Right middle lobe linear opacity appears to have been present on prior examinations , slightly more conspicuous , may reflect atelectasis or post inflammatory / infectious changes . An acute process is difficult to exclude .