Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiograph demonstrates an opacity within the right middle lobe which obscures the right heart border . The left lung is clear . There is no pleural effusion , pulmonary edema , or pneumothorax . Cardiomediastinal contours appear within normal limits .
    OUTPUT:
    
Focal right middle lobe opacity appears to have been present on multiple prior examinations though more conspicuous relative to most recent study dated ___ for which recurrence of acute infectious process is of concern .