Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest provided . Volumes are low . Left posterior basal opacity could represent atelectasis and effusion , difficult to excluded subtle pneumonia . Right lung is clear . Cardiomediastinal silhouette is normal . Bony structures are intact
    OUTPUT:
    
Left lower lobe opacity likely represents effusion and atelectasis though difficult to exclude pneumonia in the correct clinical setting .