I have 3 cats in my household and 2 of them have been vomiting and have had diarrhea since this past Saturday, May 25th. They are both indoor cats but I have recently moved into a house with a screened in porch which both have used a lot. They have never been exposed to the outdoors for more than a few minutes before the house and I think their illness may be due to the outdoors. The male is much worse than the other (female) and neither can keep food or water down for long. They vomit within a few hours of eating or drinking (which they do infrequently now). I contacted the vet and he said wait a day without feeding them anything and contact him if the problem still continues. The male had his second trip to the vet yesterday. On his first trip the vet gave me some de-worming medicine to give the cat, which he promptly threw back up. I took him to the Vet yesterday and they ran blood work and xray’s and everything came back OK with no problems at all (no blockages, no hair balls, no liver damage), the fecal tests also showed no parasites. They wanted to keep him and observe for 48 hours and see if they could get him to eat. I felt uncomfortable spending another $500.00 on top of the first $500.00 that brought not resolutions or answers. I took him home and gave him new prescribed medicine to coat his stomach, help with vomiting and diarrhea and he does not hold that down either. He is very lethargic and has no appetite at all. The female seems to be slowing improving by eating but she is still vomiting. I am not sure what to do or where to go at this point. I believe both cats have the same issue and may have a virus or parasite.

May I ask where you live? My mothers indoor cat is similarly ill with nothing showing up on the battery of tests. I wonder if it's a virus of some kind, possibly regional?

ETA: I just read about Inflammatory Bowel Disease. Seems to fit both your cats and my moms, and treatment is steroids and hypoallergenic food.

Atlanta, GA

Did they test for distemper? I know it's not common but these sound like the symptoms

Hello AJ! I would love to help. Can you tell me the results of his blood chemistry,cbc, and electrolytes. If you don't have a copy of them call your vet they can read the results to put on paper for me.
Do they free feed? ( food always available)
Water smell funny? Sulpher chlorine,,
What food do they eat, and any table human stuff too. Date/and ser. Code on feed bag
Are they from the same litter?
All treatment from the vet, and medication w/dose
Current temp.
What parasite was found on the fecal sample (the poop) to require the deworming.
Does your new home expose new air fresheners, plants, bug spray,. etc
Your screened in room home to lizards or frogs, creepy crawly bugs?
Finally look around the house anything chewed on,, 1/2 a bug or lizard, missing or broken leaves or branches on plants, was the home treated for bugs before you moved in?
All the detail you give helps! :)