Was the rug yours or was it original to the home? Even my very well mannered dog who came to me housebroken (adopted at 3) has urinated on carpets that previous cats/dogs peed on. If you haven't already rent a rug doctor. Do a dual treatment. Spray the rug down with Nature's Miracle. Then Rug Doctor with the special pet odor remover, then nature's miracle. It will put the rug out of commission for at least a day but may solve your problem.