Injured Cat

My cat turned up with an injured leg, after staying out all night (I couldn't find him anywhere). I took him to the vet, they said hes just sprained something and will be okay. The thing is he now won't lift his tail and when I touched it, he cried. I'm just wondering what may be wrong and is there any point in taking him back to the vet?

The same thing happened to my son's dog last year. I think she caught it in the back door when she went out. It was bent about 3 joints from the base. The vet felt it & thought it was just bruised. She couldn't lift it or wag it. I was so affraid she would have to have it removed. She was given pain relief & after a few days she started to lift & wag it slightly. It's now back to normal.
I would give it a couple of days & take him back to the vet if it doesn't get any better.