Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is moderately enlarged . There is low lung volumes with volume loss at the bases . The left hemidiaphragm is ill - defined and is unclear if this is due to volume loss / infiltrate / effusion . There is mild pulmonary vascular redistribution . The superior mediastinum is prominent but this may be secondary to projection . It would be helpful to the compared old films if available .
    OUTPUT:
    
Retrocardiac opacity due to volume loss / infiltrate / effusion . Prominent superior mediastinum .