Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are decreased compared to the prior exam . The heart size is mildly enlarged . The aorta is unfolded . Increased interstitial markings are seen diffusely , most pronounced within the lower lobes . Mild interstitial pulmonary edema , however , may be superimposed . No pleural effusion or pneumothorax is clearly noted . Old right - sided rib fracture is present . Sclerotic density projecting over the right lung apex could reflect a bone island within the right 1st rib . No acute osseous abnormalities are otherwise demonstrated .
    OUTPUT:
    
Increased interstitial markings diffusely , but most pronounced within the lung bases . Findings likely reflect superimposed mild pulmonary edema on a background of chronic interstitial lung disease . An atypical infectious process such as a viral infection , however , can not be completely excluded .