Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac silhouette size is normal . The aortic knob is densely calcified . Mediastinal and hilar contours are unchanged , with bilateral hilar enlargement suggestive of pulmonary arterial hypertension . Lungs are hyperinflated with paucity of pulmonary vascular markings towards the upper lobes compatible with severe emphysema . Patchy opacities in the lung bases likely reflect atelectasis , though infection can not be completely excluded in the correct clinical setting . No large pleural effusion or pneumothorax is seen , although the extreme right costophrenic angle is excluded from the field of view . There is no pulmonary vascular congestion .
    OUTPUT:
    
Severe emphysema . Enlarged hila bilaterally suggestive of pulmonary arterial hypertension . Patchy opacities at the lung bases likely reflect atelectasis , though infection can not be excluded in the correct clinical setting .