Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded . The right lung is clear . A new retrocardiac opacity is noted in the frontal view and confirmed in the lateral view . Small bilateral pleural effusions are also present . Cardiomediastinal and hilar contours are unremarkable . There is no evidence of pneumothorax .
    OUTPUT:
    
New retrocardiac opacity suggests left lower lobe pneumonia . Follow up in ___ weeks recommended to assess for resolution after treatment .