Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left base retrocardiac opacity is worrisome for pneumonia given clinical history versus less likely atelectasis . Recommend followup to resolution . The right lung is clear . . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Left lower lobe retrocardiac opacity is worrisome for pneumonia , less likely atelectasis . Recommend followup to resolution .