When I did a cursory check of her, what I found concerned me. Her abdomen was swollen. I don't mean wormy-belly-swollen. I mean full out crazy big swollen. And hard too.
Although my first hope was worms, it doesn't look like that is the cause. (Fecal is ok, no vomiting wriggly parasites, etc.) We dewormed her anyway and there is another dewormer scheduled in a few days, but her abdomen has swollen larger, not smaller.
The swelling now includes nearly her entire abdominal section. She began having a runny nose last week (sneezing, cloudy-milky fluid, drippy, etc.) and we have her on antibiotics which started on Sunday. In addition to this, the kitten doesn't seem to have grown since arriving at our house (except her abdomen of course!). Her teeth look to be that of a 3 month old kitten (which doesn't make much sense because she's been at our house for a month, at the finder's house for a month, plus however long she was with mom-cat -- assume 7 to 9 weeks).
We took her to the clinic and after examination, the vet there says that there is a very strong chance (85%) that the kitten has Feline Infectious Peritonitis (FIP). FIP is fatal. Lucky for our resident cat, it is not airborne, it travels through body fluids.
Our vet gave us few options; mainly keep her comfortable until she is in pain/discomfort ... then euthanize. We are very sad. We had been considering keeping this one since we only have our one resident cat and black cats are so difficult to adopt out.
We are planning on keeping the kitten in our house (quarantined in a crate) until she begins to show signs of discomfort. We will go through with the dewormer in a few days and finish off our remaining 8 days worth of antibiotics. We will keep our fingers crossed that our vet is wrong. I don't think she is wrong (it would be a first!), but we can hope.