My three-and-a-half year-old neutered male indoor cat has had a problem with blood in his stool for a couple of years. I find blood on the floor outside his litter box sometimes. I mentioned this to the vet a couple of times and she took a sample from him - it was yellow diarrhea with streaks of blood. Nothing showed up from the sample. She told me that with cats it is difficult to tell where the blood is coming from because cats clean themselves, but felt it could be a parasitic infection and gave him a shot. Colitis was another thought if the shot didn't work. The shot worked and the yellow "cow pats" stopped, but this morning I found, uncovered, normal-looking stool with blood on the end, and a spot on the floor. I took out the sample, but it has still has ome litter attached to it. I am wondering if I should take this in. I've asked already on two occasions about this but the vet did not seem to worried because he is eating well and very active. I don't want to subject my cat to any tests if they are not necessary. The last time I called about this, she told me again that he is not exhibiting signs of ill health.