Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Though the lungs appear clear on the frontal radiograph , on the lateral view there is an ill - defined opacity in the posterior and lower lung overlying the lower spine and is concerning for an early focus of infection , most likely in the left lower lobe . Cardiomediastinal silhouette is normal . No pleural abnormality .
    OUTPUT:
    
Ill - defined opacity appreciated only on the lateral view in the posterior and lower lung is concerning for an pneumonia , most likely in the left lower lobe . Followup radiograph is suggested in ___ weeks after appropriate treatment .