Q. My cat started to pee outside the litter box. What should I do?
A. Inappropriate bathroom use in cats is often a behavioral problem rather than a medical problem, so the first step is to have him seen by your vet to eliminate any kind of illness or condition as a cause for his defecating outside the box.
Once medical issues are ruled out, it's time to take a look at other explanations. Has there been a lot of activity that wasn't normal? Were you away and your cat was left at home or boarded? Is the litterbox located in a busy area? Has anything happened recently in this area to make him reluctant to use it again? Is there another cat, pet, or person that is preventing him from getting to the box? Have you changed it from a hooded to an open box, or vice versa? Have you changed the brand of litter or kind? Or is there something about the spot he has chosen to use that is attracting him in some way? Cats dislike disturbances to their routine and may act out as a way of expressing their dissatisfaction.
The general rule of thumb is one litter box per cat in the household, plus one. That way each cat can have a place of their own to go in case the box is occupied or another cat has claimed it as territory. They should be scooped at least daily, if not more often and changed completely on a weekly basis, and washed with soap and water.
You can also offer one kind of litter in one box and another kind in another to see if there is a preference. I don't recommend the crystal kind, since it makes a hissing sound when wet that can startle some cats and make them reluctant to use it again.
The litter boxes should be located in a quiet, low-traffic area so that the cat can use them in peace. Make sure other pets or people aren't giving them a hard time around or in the litterbox. It may take some investigation and experimentation to find your cat's preference and accommodate him so that everyone is satisfied with the situation.