Thank you CatsinDenver and NoahsMommy for responding. I don't know why I'm so concerned over this. It will be easy for me to give my Marius lots of extra love and cuddles! Thanks for the advice I sure hope everything works out.

I talked to my hubby this afternoon and asked him how Sergei looked before he left the house this morning. He said he peeked into the bathroom and he was milling around and meowing. He said he smelled pee, but didn't see anything on the floor. Sergei did smell funny when we picked him up from the vet this morning, but I just assumed it was surgery smell. I sure hope this cat knows how to use the litter box! I know Aaron definitely will not allow another cat with bathroom problems in the house. One is enough. So, cross your fingers and pray for us that everything will work out!
I've been wondering about Sergei all day today!
**hugs**