If you are talking to me, she needed the surgery right away. Take a look at the pic I attached. That's how big her stones were. there were FOUR of them, and she is an 7.5 lbs dog. This is the result of neglect from her original owners when it was just a mere UTI, then crystals. She was not feeding her the crystal disolving food, she was feeding Beneful!
If he does need surgery, and no one will be at the hospital overnight, then I agree with what the others have suggested, schedule the surgery for Thursday, take off Friday and Monday if you can. Good luck with the tests.