Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Small left apical pneumothorax persists since chest tube removal , appears to have increased slightly since chest radiograph earlier on the same day . Improved lung volumes bilaterally . Right base atelectasis has improved . Linear atelectasis seen in the left base with retrocardiac opacification which may be a combination of pleural fluid and volume loss . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Small left apical pneumothorax , appears increased compared to chest radiograph performed earlier on the same day . Retrocardiac opacity may be combination of pleural fluid and volume loss .