The inside of your home is the den and pack animals naturally like to keep their dens clean. They will want to relieve themselves as far away as possible from where they eat and sleep. I wouldn't regard it as a problem, per se, he is doing what comes naturally and cleaning up. Can you install a dog door? If he is having trouble holding on, it could be a urinary tract infection, or just that he needs to be taken out more frequently. *I will find a link and quote*