When Raven was alive, he had problems with the feline version of Interstitial Cystitis. He had many x-rays done, even an ultrasound, and many rounds of antibiotics (so many he developed an intolerance to Clavamox).
What worked best for him was as much canned food as we could get him eating (you may not like it, but a prescription or OTC urinary diet may be what he needs to be stabilized--ingredients aren't the important thing right now, getting him stabilized so you can transition back is the important thing). Raven like Max Gourmet Classics (the little cans), Pro Plan Urinary Health (it's chicken in gravy). We tried but he didn't like Friskies Special Diet. That has the same target pH as all other purina foods labeled for Urinary Tract Health (6.3). We did try Pro Plan Urinary Health last year, but the dry has something in it that doesn't agree with Nabu. And my crew has been stable for so long, I just check pH levels of foods before commit to buying them.
We used Cosequin for Raven's bout in 2004. He was also on Amitriptyline for 4-6 months that year. Amitriptyline has properties that help stop the bladder from making them feel that urge. The cosequin helps reline the bladder with the protective tissue. We also used Feliway diffusers at that time. I bought a water fountain for the guys in 2003 I think. (we've tried all the brands since then, and settle on the Drinkwell)
For Raven, concentrating on adding wet food within acceptable ranges to his diet and making sure his dry food was withing ok ranges helped. His last one though, I really think the Amitriptyline broke the cycle.
See Raven would get a recurring bladder infection, and it could go on for months. Our vet in Southern California was very understanding, and after ruling everything out--told us to call when Raven was getting one adn he would dispense meds. Well, once he got out of a UTI cycle, he could be stable for months or years. They were really triggered by stress, and he was a high stress cat, so we did our best to minimize it.
Raven had crystals (struvite) in 1999, and 2000. Everything else was of unknown origin. Nabu has had crystals (98/99/00, they always cleared up quick--but I only fed dry at the time; since I feed 50%+ wet he is fine now), and bacterial UTIs, but not the Interstitial Cystitis that Raven had. Stimpy was completely blocked before we adopted him (2002), but I'm 99.9% sure that was related to cheap food. He's also been fine since.
I hope that's not too long...I wrote more than I planned.