Kirsten, I'm so sorry these problems just keep going on and on. I sure hope you find some sort of solution soon so poor Luna (and poor you!) have some relief.

The only thing I can think of is to have an ultrasound of the bladder. My only experience with any of this is with Peanut still having blood in her urine a a few days after the start of antibiotics. The vet did an ultrasound and discovered a tumor in her bladder. He operated to removed the tumor - ended up removing 1/2 her bladder, but got the tumor and all surrounding nasty tissue. As you may or may not remember, during her follow-up appt. the vet said there are still abnormal cells in her urine indicating "a malignancy somewhere" but he said there was nothing more he could do and we just have to keep an eye on her to see if/when the "malignancy" gets worse.

But my point is, he did the ultrasound and that showed what the problem was right away, so maybe this would help with Luna?