How does the vet test for UTI's

My stray cat, Fluffy, who I've had 1 1/2 years has recently been peeing on the carpet. Maybe she's been doing this all along as I saw small spots on the steps. I also have two other cats and never had a problem. Fluffy & resident cat #1 have never gotten along, but #2 cat & she do. I have two litter boxes one on each floor, only have 4 rooms. Cat #1 has been sleeping on top of one of the boxes so I put something on top so she could not get comfy I figured that Fluffy didn't want to use that box for fear of fights. This AM fluffy peed right outside this box on a small rug, then not too long after I heard her scratching in the box. She always poops in a box. I clean them every day. Its hard for me to clean up after her as I have a back problem. So my question is How does the vet check for a UTI? I'm calling as soon as the office opens. I hope its not a complicated process since I can't chase her around the house. I don't want to get rid of her since thats not what I rescued her for. Advice please.

I just took 4 of mine in this AM to check them for UTIs. While no one is peeing outside the box, there is an abnormally strong urine odor in the cat box.

My vet sometimes can palpate the bladder & get urine that way, but otherwise does a cystocentesis. (I do so hope I spelled that right ) He then has a vet tech test the urine, checking the pH, specific gravity, for any presence of blood, glucose, & also checks for crystals.

You can also get your cat to pee on non-absorbing litter, or tiny seed beads (available at your local craft store); sometimes newspaper works; fine, quality aquarium gravel, depends on the cat.
Immediately after your cat pees, syringe it up and put it in a plastic jar (both available at your vet or maybe a really good pet store). Refrigerate. Take to vet.
But the vet doing it is the best way. Course then you have to get the cat into the cat carrier. For me, obtaining the urine sample myself was the easier way.

Always good to get the vet check - did you say she's peeing right outside the box? Have you changed litter recently? I've often read that when a cat is peeing right outside it's box, you may want to check:

• type of litter (especially if it's a recent change)
• cleanliness of box (some kitties really really like the box to be scooped a lot - at least twice a day)
• number of boxes - rule of thumb, if you can, one box per cat plus one extra) - I happen to have four of the large Walmart boxes (not too big, really) for two cats

Also, I swear by Cat Attract litter by Dr. Elsey - at least to try. You can get it at PetSmart, etc.