Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to the prior study , there is indistinctness of the lung bases , likely due to pleural fluid at the posterior pleural surface . The visualized lung parenchyma is clear and the cardiac and mediastinal contours are normal .
    OUTPUT:
    
Indistinctness of the lung bases may be due to pleural fluid in the posterior sulcus . A lateral view would be helpful to exclude a small pleural effusion .