[kjc]

That looks to be a good food... but best to get specifics from your vet... like which ingredients to avoid, or reduced ash /magnesium depending on the specifics of his problem.

I will venture to say that infection usually accompanies struvites, but I can't seem to find that article at this moment... it may have been in a thread on here somewhere.
So let us know what the vet says and we'll be able to make more specific suggestions.

In the meantime, you can add a bit more water to the tinned food to increase his water consumption.