Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are normal . An opacity is located in the superior aspect of the left lower lobe . Cardiomediastinal contours are normal . The left hilar contour slightly enlarged which could be due to reactive lymphadenopathy or less likely a central mass / obstruction . No pleural effusions and the pleural surfaces are normal .
    OUTPUT:
    
Left lower lobe pneumonia . Recommend follow - up in 6 weeks to confirm substantial clearing and exclude persistent infection and / or central obstruction .