Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral radiographs of the chest . The heart is mildly enlarged . The cardiomediastinal silhouette and hilar contours are stable . Retrocardiac opacity likely related to atelectasis ; however , pneumonia is not excluded . No pneumothorax . There is a moderate left pleural effusion and small right pleural effusion unchanged from prior . There is pulmonary vascular congestion . No displaced rib fracture identified .
    OUTPUT:
    
Retrocardiac opacity likely represents atelectasis ; however , pneumonia is not excluded . Moderate left pleural effusion and small right pleural effusion unchanged from prior .