It only lasted that one night, but we figured we should get her checked out anyway since this was also what she did when she had stones in her bladder. That time she had blood in her pee, this time there wasn't any visible blood, but who knows. We didn't want to make a vet appointment and drag her to the vet only to be told they needed to keep her to get a urine sample, so we asked when we went in to get more of her special food.
Because of the problem she had a few years ago, she's been on a special catfood diet. She only eats the Waltham SO Urinary formula (wet and dry) and we can only get it from a vet. When we went in to get another batch of the food, we asked if it could be a UTI or other problem and if it was a UTI if it could have cleared up on its own.
The vet's assistant/nurse/I-have-no-idea-what-her-t
We were supposed to take this kit home, empty the litter box, wash it thoroughly and then put in just the plastic pellets. I was dubious, but we followed instructions and after a few hours, emilytheslayer noticed Copper had used the box! I used the eye dropper to suck up the pee a tiny bit at a time and put it in the cup. We then sealed the cup in a (provided) ziplock and put it in the fridge while I cleaned out the box and put actual litter back in it.
The next day, emilytheslayer took the pee to the vet and they tested it. Near the end of that same day I got a call from the vet's office. No crystals, no blood, Copper is fine! W000!
I'm gusesing that when she wasn't feeling well, she drank lots of water and peed a lot and cleared out the infection. That's exactly what humans do when they get an infections (usually), so I see no reason it shouldn't work for a cat.