Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Low lung volumes . Stable enlargement of the cardiomediastinal silhouette . Vascular congestion without overt pulmonary edema . Opacification at the left lung base may represent atelectasis , however a developing pneumonia is a consideration .
    OUTPUT:
    
Opacification at the left lung base , which may represent pneumonia , however underlying pneumonia can not be excluded .