Pets can indeed be a handful and then some. We need to cherish them, but we also need to clean up after them. There are some steps to follow if you want an absolutely clean area. Find every soiled area, use a black-light if necessary; clean the soiled areas appropriately to remove odors; rule out medical causes by visiting the vet; find out why your pet is passing waste in inappropriate locations. Making the "accident zone" unattractive to the pet, hence, retraining them is last, but not the least of the steps to be taken.
Link: Removing Pet Stains and Odors | The Humane Society of t