Vet asap like the others say. That is an emergency and looks like a probably bowel tear from being impacted or something like that. Get your Leo medical attention like, yesterday!
My Leo actually started to do the same thing.....funny about it is that it didn't start until after being seen by a vet for eye issues. I suspect my Leo could be stressed from excessive handling (medications). Waiting on a test from a vet to determine the cause of it. Have you discovered the cause of yours?
I'm guessing since this thread is quite old that this user has not replied to this thread either because they forgot about it or they didn't take the Gecko to the Vet and it passed. :/