Hi! I Am Currently On The Process To Be Hire

Hi! I am currently on the process to be hire for my new job. I am done with the basic medical exams after that i was advised to repeat my urine test and also done with the KUB ultrasound and the extraction of blood. Now they told me to get a Nephro clearance.May i know what is the meaning of it, will i be going to take some new test or just to have a clearance that i am going to be fit to work? Thank you.