shih tzu peeing in the house

Question
Hi, i have a 3 year old shih tzu. female. I previously had her trained to go outside. she always scratched at the door or whined to go out and pee. Now all she does is pee in the house in front of my bathroom door. I clean it and spray it with the odour killer. I correct her and tell her it is bad. I take her outside and if she does go i reward her and play with her and give her a cookie. She will hold her pee for sometimes 24hrs. It is like she is just waiting to go in the house. I spend most of my time telling this dog to go pee and it is sooooo frustrating. I have no idea what to do next. she really REFUSES to go outside. I cannot believe it. Please, what can i do. Thanks

Answer
Sarah,
There could be several answers depending on issues.  1)she could have an infection See your vet.  2)any changes she could be acting out from separation anxiety (shih tzu's are well known for this behavior).  They also do not take well to being reprimanded and shamed it seems to enforce the behavior you are trying to correct.  The best thing to do is to when you notice that she is starting to go to that place to urinate take her out to potty just like when she was a puppy and then reward her for it.  Basically retrain her!  If she is doing this when you are away from home you may have to confine her to one area of the home.  Is she spayed?  
Has there been another dog that has marked in the home?  There are so many reasons for the behavior.  But, right now to correct the problem, most cases it is better to ignore her bad behavior clean it up and not acknowledge it to her..that way she sees she doesn't have the upper hand with frustrating you.  But I would take her to the vet and make sure there is not a medical reason like an infection or anything else going on as well.  I would also limit her available water intake and like I said treat her as if she were a puppy and when she eats or drinks take her out within  30 minutes and no free grazing of food or drink until she gets back to her correct behavior.  Hope this helps.