Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since the prior radiograph , there has been slow progression of disease with worsening diffuse interstitial abnormality , particularly in the right upper lobe and left perihilar region . In addition there are new bibasilar opacities . There is no definite focal consolidation , pleural effusion , or pneumothorax . The cardiomediastinal silhouette is unchanged . There are no acute skeletal abnormalities .
    OUTPUT:
    
Progression of disease , particularly in the right upper lobe and left perihilar region . The lack of intervening study since ___ makes it difficult to determine if this is an acute exacerbation or slow chronic progression .