you should first consult pulmonologist and get pleural fluid aspirated and test to be done on that fluid. whatever the result of pleural fluid testing we can start medicine according to that

hi, we need to find out cause for pleural effusion as its the treatment of cause will treat the effusion ; pleural effusion is treated as immediate as removal of fluid directly by tapping (by needle ) if he is having severe breathlessness and its compromising breathing but if this is not the case then we need to check the fluid as well as find out cause of fluid collection ; please provide details about his testing and lab reports ; if not done then do it urgently .

first if all find out the cause, either TB or at this age, there may be rare possibility of Cancer, so show to Physician or chest physician