FINDINGS:
A new moderate to large right pleural effusion is demonstrated with associated
 right basilar opacification.  Patchy left basilar opacity is also
 demonstrated.  Peripheral increased interstitial markings likely reflect
 underlying chronic interstitial lung disease, as assessed on the previous CT. 
 There is no pneumothorax or pulmonary vascular congestion.  Heart size is
 difficult to determine given the presence of the left pleural effusion. 
 Mediastinal contours are unremarkable with calcification of the aortic knob. 
 Right hilar enlargement is suggestive of underlying lymphadenopathy.  There
 are multilevel degenerative changes in the thoracic spine.

IMPRESSION:
1. New moderate to large right pleural effusion.
 
 2. Right basilar opacification could reflect pneumonia, atelectasis, or
 aspiration.  Followup imaging after treatment are recommended to ensure
 resolution and exclude underlying malignancy.  Milder opacification within the
 left lung base may reflect atelectasis or chronic interstitial abnormality.
 
 3. Chronic interstitial lung disease, better assessed on previous CT.