new kitten, older cat

I brought home a 3 month old kitten a week ago and have kept him seperated from my 4 year old cat until they get used to each other. I have 3 litter boxes so they each have their own and keep them very clean. The thing I am wondering about is the fact that the older cat isnt using the boxes,yet I have looked in every nook and crany of the house and cant find any evedence he is going anywhere else! He has always been good about using the boxes. I know he is upset about the kitten but is slowly getting used to him, he gets a little closer to it everyday. Is it possible he is just not going ? I have an appointment with my vet on monday but wondered if anyone has ever heard of this problem.

Well to be sure - I'd confine him to one room with a litter box - that way you can tell if he's going or not this weekend.

I would keep them separate till vet visit, kitten confined in one room, dominant rest of home. See what your vet says and take it from there!