Blood in Cats Stool

Question
I have 2 cat's.  1 is a domestic long hair and the other is short hair.  Tonight while cleaning the litter box we noticed that one of them had a very bloody bowel movement. It was pretty fresh and I checked both of them to see if I could see any traces of blood on either of them and couldn't.  So I'm not sure which cat that it is, but I'm not sure what could cause it.  Any suggestions?

Answer
This is usually a temporary thing from some irritation of the rectum.
Having a lot of hair in the stoll can cause this, changes in food, etc.

If the cat strains to hard during the bowel movement that can cause this also. Some small vessels are ruptured near the rectum inside and that causes the 'frank' blood you are seeing.

Unless you see it more than two days in a row it is usually not something to worry about. If you do, or it gets worse or progresses to diarrhea, then it's time to call the vet and make an appointment.