Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP single view of the chest has been obtained with patient in sitting semi-upright position . Analysis is performed in direct comparison with the next preceding similar study obtained five hours earlier during the same day . Apparently , a left - sided thoracocentesis was performed as there is now clearly diminished left - sided basal density with partial visibility of the left - sided diaphragm . Several linear densities indicating plate atelectasis remain . No acute pulmonary infiltrates or masses in the left upper half of the left hemithorax . No pneumothorax is identified . The degree of mediastinal shift towards the right has decreased mildly but is generally still present . Status post sternotomy , bypass surgery and mitral valve prosthesis placement , as before .
    OUTPUT:
    
Successful left - sided thoracocentesis with diminished amount of fluid and no evidence of pneumothorax .