Group Insurance Help?

I have a kidney stone and I don't have insurance. I went to a urologist and he confirmed the stone with an x ray. Its a huge stone in my right kidney so the doctor said I will need lithotripsy to break up the stone but it will cost thousands of dollars that I don't have. So he told me to try my local hospital b/c they have a discount program. So after waiting months I finally got approved but I still have to pay 20% but even with the discount I still cant afford the procedure.(Its still a few thousand dollars!!!) My jobs open enrollment for the company group insurance is coming up but I'm worried they wont cover it b/c it will be a preexisting condition. Is there any way I can get my insurance to pay for the procedure? B/c I can't afford it on my own. Please help.. Thanks.