I'm really sorry that you are dealing with such a sudden onset of a horrible illness...whatever it is. I know how it turns your world upside down!
My Zoey was diagnosed with FIP last March. We ended up putting her to sleep because she couldn't fight anymore, but I'm still not sure that she actually had FIP. In any case, I learned a lot about FIP while dealing with Zoey's illness, so hopefully I can give some information that could be of help.
You may know this, but FIP is very hard to diagnose, and is often misdiagnosed. I am not saying that your poor kitty (name?) does not have FIP....but just be a little weary of the diagnosis. I just feel that FIP tends to be the "we don't really know what's wrong" diagnosis for vets. We can't prove that they don't have it, so why not use this diagnosis? It's not good enough for me and I would definitely be trying to get more tests.
Please look at post #7 of this thread...it is quite long, but really sums up all my thoughts about FIP....most of it was written back when my experiences with Zoey were ripe in my mind (I'm a little foggy about everything now): http://www.thecatsite.com/forums/sho...&highlight=FIP
The sudden onset is a symptom of FIP...it happens very quickly. I think my Zoey had problems with her eyes...or so the ER vet (who was...I'm sorry...an idiot) told me...but her eye problems seemed to go away after a day (my vet said she was seeing fine). She had difficulty walking. Neurological problems can be a symptom of FIP. As can fluid build up, but usually it is in the abdomen, not the lungs.
Never in all my reading about FIP have I heard about pus coming out of the ears. And typically cats have a persistent HIGH temperature with FIP...so it strikes me a bit that your girl has a low temp. However, FIP is a strange disease with various manifestations...I'd still be looking at differentials.
What tests have already been done? If it were me, I'd be getting:
- a full blood workup - including serology to check proteins (specifically alubumin/globulin - these often get out of whack with FIP)
- a coronavirus titre (although a positive titre DOES NOT mean she has FIP - but it will give you some indication of whether it is a possibility)
- a swab of the fluid in her ears (and whatever tests they can do on it....it sounds like she could have an infection of some sort....difficulty with balance/walking can go with ear infections)
- x-rays or ultrasounds, especially of her chest
- if you have the means, some sort of picture of her head....although I'm sure you'd have to go to a specialist for this
- ask for information about antibiotics/steroid treatment - yours is a tricky case in that your kitty has a low temp (usually high temps go with infections), but I would certainly be asking about it....
Please visit and post about your kitty at this group: http://pets.groups.yahoo.com/group/FIPCatSupport/
. The people there are VERY knowledgeable about FIP and can often give differentials about what else to test for.
I hope this helps and
that you get an answer soon, and that the answer is not FIP.