Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable upright chest radiograph demonstrates chronic interstitial opacity most prominent at the bases , with decreased lung volumes in comparison with prior . The cardiac silhouette is normal in size , the mediastinal contours are normal . There is no pleural effusion , or pneumothorax .
    OUTPUT:
    
Decreased lung volumes compared with prior , chronic interstitial abnormality , which may reflect chronic edema , or chronic interstitial lung disease .