Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded . There is a retrocardiac opacity which is confirmed on the lateral views . Mild peribronchial thickening is present . Cardiomediastinal and hilar contours are unremarkable . There is a tortuous aorta . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Left lower lobe pneumonia . Follow up radiographs are recommended after treatment to ensure resolution of this finding .