@Quercus:
I don't know if this is at all accurate…but his theory made sense to me. Also, some Bs are prone to crystal formation, but often don't develop a full blown UTI. There is something that some folks add to the water to change the PH of the urine, but I don't remember what...maybe someone else can help me out with that.
I was told that crystals were a sign and led to kidney stones?–not necessarily a sign of UTIs? There were special dog foods for this--to keep crystals from forming because I had to use one at one time (this was about 10-12 years ago), but my vet told me that the good quality dog foods now are formulated to avoid crystal formation, so you don't usually have to get special food.