Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is borderline enlarged . The mediastinal and hilar contours are unremarkable . Focal opacity within the left mid lung field , likely within the superior segment of the left lower lobe , is concerning for pneumonia . The right lung is clear . No pleural effusion or pneumothorax is identified . There are no acute osseous abnormalities .
    OUTPUT:
    
Left lower lobe pneumonia . Follow up radiographs after treatment are recommended to ensure resolution of this finding .