Cause of a UTI

Question
We're taking our puppy (18 weeks) to the vet tomorrow for a possible UTI and I'm wondering what are the possible causes?  Sine it's a holiday our vet is off, we did speak to him on the phone and he said to bring him in tomorrow.  We're overly cautious of our dog so we're not sure how this could've happened?  Also what will they do to test him?

Answer
UTI's are fairly common.  I don't know there is much you can do to avoid them. If they occur very often, the vet will prescribe Science C-D or other diet to make the urine more acid and less friendly to the bugs.  

The vet will at least palpate the bladder, and maybe check a urine sample.  A course of antibiotics usually clears it up soon.