My pooch had very high pH wee which lead to crystals... lead to a UTI. Vet did say it could be kidney stones, but more likely diet related as she was a young dog.
She had antibiotics and a change of diet to try and lower the pH. She was on a fish based kibble (which she adored, lots of feeding problems, now food allergies).
I made sure she had lots of water to drink (added to her food etc) and measured the pH of her wee with test strips (bought from chemist, but amazon would sell them). At the time she would only wee at home, so after a walk would be busting, and I could easily collect/test.
Now not so easy, but I test the grass where she's peed rather than concentrating on getting a "good" sample. I only keep testing as I bought 100 strips and her diet is changing as we try to sort out food allergies and I am vaguely keeping track of what works.
I would complete the antibiotics, make sure she drinks lots, buy some wee pH strips and test (lower than 8 desirable). Change diet, see if pH changes and symptoms stay away.
If symptoms come back, go down the route of xray etc. If antibiotics and diet work, then saved cost and stress of procedure.