Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: In comparison to ___ chest radiograph , the previously seen small left apical pneumothorax and left lower lung atelectasis have resolved . Blunt left costophrenic angle may represent small left pleural effusion versus pleural thickening . The cardiomediastinal and hilar contour are normal .
    OUTPUT:
    
1 . Previously seen small left apical pneumothorax and left lower lung atelectasis have resolved . 2 . Blunted left costophrenic angle may be secondary to a small left pleural effusion versus pleural thickening .