KIDNEY STENT INSIDE ME FOR TWO YEARS NOW; WHEN SHOULD IT BE

I WAS TREATED FOR KIDNEY STONES ABOUT 2 YEARS AGO. MY UROLOGIST COULD NOT GET ALL OF THE PIECES OUT OF MY KIDNEY, SO HE INSERTED A STENT, TELLING ME THAT THE STENT WOULD HELP IN PASSING THE REMAINING STONES. I HAVE NOT HAD ANY PAIN TO SPEAK OF, IN THE LAST 2 YEARS BUT HAVE URINATED BLOOD 3 OR 4 TIMES, WHEN SHOULD IT BE REMOVED ? ANY RESPONSES WILL BE GREATLY APPRECIATED . THANK YOU , DRISKY