I'm going to copy and paste what I said recently in another thread. I hope it helps. Make sure you rule out other possibilities (toxoplasmosis, bartonella, etc.). I guess hope for the best, but expect the worse. Get a second opinion. Zoey hasn't been doing well the last couple of days (likely because she was taken off the antibiotics despite a very high white blood cell count)), but I still feel like the research and effort I have put into her is worth it. FIP is a very tricky diagnosis - and my experience thus far is that once they get that label, it's hard to get new vets to ignore it, even if blood results aren't indicating it. Zoey is very sick....but I don't think she has FIP. That said, there are lots of cats who are diagnosed with FIP and do actually have it. It's a very fine line, but I think as long as your cat has some fight in her, you need to give her a chance.
for you and Babe. I truly hope this is not FIP and that she is doing better!
"I am very sorry that you have gotten this bad news about your kitten!
However, I am with those suggesting that you be cautious about the diagnosis. I'd guess that biopsy results are significantly more reliable than blood tests, but unless they are absolutely sure, I would be hesitant to put a cat to sleep before giving it a chance to recover. Sounds like you've changed her diet to a new protein source, which is great. If she's getting better, just see how she does. If she's been through surgery and everything else, it might take her a bit of time to emotionally recover. Until you see her suffering, I would see how it goes. I have never been through this, but most say that the cat will "tell you" when they are ready to go.
My little Zoey has been through a lot in the last 4 weeks, including an FIP diagnosis. At first, I was hesitant to accept the FIP diagnosis, but after doing a lot of research, and seeing her progress, I accepted it. Then, she started getting better and it became evident that she had a broken tail (missed on initial glance at the x-rays). Explained many of her symptoms, but not all. In my opinion, the latest blood work does not indicate FIP. It indicates some other sort of infection, possibly an ear infection (she was treated for ear mites at the vet, but her ears are still really gunky). I never gave my vet the chance to suggest I put her to sleep, but I know he was giving me that possibility by the way he spoke of treatments - he called it palliative care. There was one day that I would have very likely put her to sleep (based on the reports of people I had checking on her, she appeared to be suffering more than I had seen), but luckily I was at work that day and she was much better by the time I got home. Then, her eyes were acting wonky one day and an emergency vet suggested we put her to sleep (despite blood work indicating that she was improving). If I would have PTS on any of these occasions, I would not have seen Zoey walking normally, eating well, playing, and "talking" as she is now. She is not yet back to her old self, but everyday I feel we make a step back toward normal.
The reason I talk about Zoey so in depth is that I truly felt that I needed to give her a chance to recover from everything that was going on with her. FIP is such a difficult disease to diagnose, and there are many treatable things that it could be mistaken for. Make sure you are confident with the diagnosis before making and decisions, and don't put her to sleep because you fear she might get worse. Cross that bridge when you get there. Even if you are expecting the worst, you might be pleasantly surprised by the best!
Do her blood results indicate that she may have FIP? Albumin/Globulin levels, anemia, lymphocytes? FIP titer (not that I'd trust this for anything...)? The more evidence the builds, the more likely the diagnosis.
Edited: To add to what Blaise said, I joined that particular FIP group when I was dealing with Zoey. Through that, I found http://pets.groups.yahoo.com/group/FIPCatSupport/
, which gets a bit more activity. I think many of the people posting on these groups are the same. However, they are EXTREMELY helpful. If you post blood and test results, they will help you interpret them. They will give you differentials to check out. They will suggest possible courses of action as well. If Pix does have FIP, they will provide great support for you as her disease progresses. Please check the two groups out!"