Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac silhouette size is normal . The aorta is mildly tortuous . Mediastinal and hilar contours are otherwise unremarkable . The pulmonary vasculature is normal . No focal consolidation is identified . Increased interstitial markings are noted at the lung bases , similar to that seen on the previous exam . No pleural effusion or pneumothorax is identified . Mild degenerative changes are seen in the thoracic spine as well as within the AC joints bilaterally .
    OUTPUT:
    
Increased interstitial markings within the lung bases , similar compared to the prior exam . Findings may be due to mild volume overload but an atypical infectious process is not excluded .