As someone who's really had to be careful to keep magnesium out of her cat's system, I'm going to respectfully disagree on the Milk of Magnesia. It's only one kind of urinary dysfunction, and only some cats are susceptible, but it hurts and it's scary and worth avoiding.

You could goop some vitamin E on it - there's no known toxic dose in the cat, and it does help with healing. But definitely ask a vet.

Love, Columbine