Our cat is a male, indoor, 11 year old cat. He sometimes in the last couple of months has been deficating outside of the litter box, of which he also uses the litter box. He use to have a pretty solid stool, but lately I have noticed that it has turned quite soft, almost runny. Not like diarreha though.I noticed tonight that his rectum area looks inflamed, and while putting a slight warm cloth on it to clean away what looks like dried stool I saw some yellowish puss come out of his rectum when he moved. I am going to take him to the vet, but we also have 2 dogs, and I am concerned that if he has something it may be contagious to our canines. Can you help out and tell me what may be the cause of this puss and inflamed rectum. As well as the deficating outside the litter box now and then?