Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac , mediastinal and hilar contours appear unchanged including mild cardiomegaly . There is a patchy left mid lung opacity , although elsewhere , the lungs appear clear . Lung volumes are again low . There is no definite pleural effusion or pneumothorax . Moderate degenerative changes involve the each acromioclavicular joint .
    OUTPUT:
    
Vague left mid lung opacity . Pneumonia is not excluded but evaluation of the chest with these films is limited . Short - term followup radiographs may be helpful to reassess . In addition to the possibility of infection , patchy atelectasis could be considered and resolving vascular congestion .