Cat rectal discharge

I have a 5yo male nutered cat who never goes outside. Today I have noticed a milky liquid dripping from his rectum. At first I thought it was worms which my dog had not too long ago but turned out to be a liquid. I know alot about dogs but not much about cats. Can you take a guess at what this may be? Were going to the vet tomorrow morning but I am very worried tonight.
Thank you for your time ...KK

[horsey_girl]

I have a 8 year old 21 pound siamese cat.  Ive had him since he was a kitten out of a litter at my grandmothers house.  He loves me to death and we all know that I am his and he is mine.  I am assuming it is discharge, because i have not quite SEEN it come from any "hole", but it smells SO bad... what else would it come from? So, i've thought that the discharge might be some kind of "love" juice or something.  Like a way for him to express his enfatuation with me, by putting his "juice" on me....?  Im not sure.. I need answers!