Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Small bilateral pleural effusions are persistent , with a retrocardiac opacity which may represent atelectasis or pneumonia in the appropriate clinical setting . Left chest wall pacemaker and leads are appropriately positioned . The aortic knob is calcified and the median sternotomy wires are intact . Lung volumes are slightly reduced compared to the prior study . Moderate size hiatal hernia is again noted .
    OUTPUT:
    
Small bilateral pleural effusions and retrocardiac opacity which apart from the hiatal hernia , may represent atelectasis or infection in the appropriate clinical setting .