Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A small right pneumothorax has markedly decreased in size following placement of a right thoracostomy tube . There is improvement of mild leftward shift of the mediastinum . A small left pleural effusion is unchanged .
    OUTPUT:
    
Small right pneumothorax has markedly decreased in size following placement of a right thoracostomy tube .