If you have not brought any new cats into the house in the past 6 months or so, I would still put FIP at the bottom of the 'worry' list. If he has always been healthy, that's another plus. FIP tends to affect cats with poor immune systems. If your vet makes house calls, I would try to get him to come out rather than subjecting your boy to the stress of going to his office. Most vets WILL make housecalls - they just don't advertise the fact. Let me know how things go. It's good that his kidneys seem to be functioning well!
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Lori McLaughlin
Your veterinarian should ALWAYS be consulted first and foremost when your pet's welfare is at stake.