My age 25, I had pain in lower left back then my doctor suggested to ultrasound abdominal, it shows small kidney stone and I take medication for 20 days and after once again i went to ultrasound​ abdominal in that report no stone but there is mild pleural effusion, but x ray shows nothing,and i dont have any symptoms related to that,if there is a mild pleural effusion will it increase or cure on its own and how i know it is increases, does it cure quickly when​ it is mild pleural effusion