Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is normal . The hilar and mediastinal contours are within normal limits . The aorta is moderately calcified and tortuous . A left lower lobe opacity is present , obscuring the costophrenic angle , which may represent a small focus of pneumonia . There is no pneumothorax or large pleural effusion .
    OUTPUT:
    
Left lower lobe pneumonia .