Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are slightly hyperexpanded but clear . The heart is top normal . The mediastinal and hilar contours are normal . There is no pleural effusion . Lucency along the right hemidiaphragm is of unclear etiology , but could reflect pneumothorax .
    OUTPUT:
    
Question of pneumothorax at the right base is not confirmed on follow - up CT of the abdomen and pelvis obtained at the time of this dictation . No evidence of pneumonia .