The blood is bright red and the stool is "standard issue", so you are correct in that it is coming from the lower intestine or rectum area. When he had the infection he had crystals, but they disappeared after a month of antibiotics and the vet didn't see anything last week when she looked.

I don't think that it is IBD, because one of the other cats (Tanner) has IBD so I converted everyone's diet over to something he could he (it saves on the hassle factor).

The vet still has not phoned, but I also know that she does surgery in the mornings so it may depend on when she finishes everything before I can talk with her.