Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiographs were obtained . A left lower lobe retrocardiac opacity is seen on both the frontal and lateral projections . No effusion or pneumothorax is present . The cardiomediastinal contours are normal . Surgical clips project over the neck .
    OUTPUT:
    
Left lower lobe pneumonia . Follow - up radiographs should be obtained in ___ weeks to ensure resolution .