Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low causing crowding of the central bronchovascular structures . There is a left retrocardiac opacity with air bronchograms concerning for pneumonia given the clinical setting . No pleural effusion or pneumothorax is seen . The heart is normal in size given AP technique and low lung volumes . Irregularity and shortening of the right clavicle is noted .
    OUTPUT:
    
Left retrocardiac opacity concerning for left lower lobe pneumonia .