It sounds like the tumor in his small intestine is causing a lot of fluid to be released in that area, just as the cat I had with lung cancer had to have his chest tapped frequently. My vet recommended pumpkin pie filling in the past for cats with diarrhoea. Have you tried Metamucil? Also, I think cats can take some human medicines for diarrhoea as long as they don't contain tylenol - but I could be wrong.

I know what you mean about spreading tarps around. The isolation rooms for my kitten with C.H. (pretty much confirmed by my vet tonight) have most of the floor covered with plastic, though she still finds the small areas of carpet to pee on. I don't blame her, I think the carpet makes her feel more secure because she gets better traction on it. I'm so sorry about what you and Miles are going through.