Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal inspiratory and expiratory and lateral chest radiographs demonstrate interval removal of a left pigtail catheter . The left apical pneumothorax is persistent and similar in size . The remainder of the exam is unchanged .
    OUTPUT:
    
A persistent left apical pneumothorax is unchanged after removal of a left pigtail catheter .