Hi there,
Keep an eye on it and if it doesn't clear up in a couple of days you should see the vet. How old is your cat? They can get some nasty problems with their gut and diarrhoea is sometimes the only symptom. Not wanting to worry you, because it's still rare, but we lost our 12 year old tabby to a lymphoma and all she had was a runny bum!
Here's to good health

__________________

Mummy to 1 puppy, 3 cats, 3 chickens, 2 guinea pigs and 2 small children