Diarreah in cats

Question
What can cause sudden diarreah in an otherwise healthy cat.  He has had bladder problems in the past, so I MUST feed him Science Diet prescription food from the Vet.  He is still very lively and seems to be fine otherwise. We just moved to a new home, so could that maybe be the cause.  I KNOW if it persists until tomorrow I WILL take him to the Vet.  He IS my baby though,  and I just wanted to ease my mind a little and get a little reassurance, if you can afford me some.  

Answer
It could be viral, bacterial, toxin, parasites or due to another underlying illness.  Best thing to do is fast him for 24 hours, then introduce some boiled chicken with rice or meat baby food AND YOGURT....hold off on his regular food until stool is normal for 48 hours, then reintroduce it by mixing with the bland diet for 3 more days.