Hello. I'm replying to your comment on my answer here because my computer seems to dislike replying on the comment at the minute. It definately does sound like there is something wrong with her kidneys; my cat reacts in a similar way if you touch her anywhere from the end of her back to the tip of her tail and the vets said it was to do with her kidneys. They're keeping an eye on it at the moment and they gave her some medicine to take. They'll probably do the same for your dog unless it's more serious. Of course it could be something else entirely but it does sound similar.