Even if the history doesn't quite fit with a medical problem, it may be suggested to perform a medical work-up to make sure that no problems are seen. This could include basic bloodwork (complete blood count, blood chemistry, thyroid hormone) and then a more detailed analysis of the urogenital system (urinalysis, urine culture, imaging of the urogenital tract with either radiographs or an ultrasound).
If a medical issue is ruled out, then the problem may be more of a behavioral issue. Behavioral issues can be broken down further into issues involving marking versus litter box training or aversion issues. An indication that problems with the litter box may be a marking issue would be if the history includes:
1.) Urine spraying on a vertical surface
2.) Problem started after a change in the household (new roommate, new furniture, recent visit from friends/relatives, new pet)
3.) Accidents occur around a window or door
4.) Accidents occur on owner's bed or clothes
5.) Accidents tend to occur in a similar spot
6.) The pet is defecating in the box, but not urinating in the box.
7.) The pet sometimes urinates in the box, but sometimes urinates outside the box
These histories tend to indicate more of a territorial or anxiety issue and the cat trying to assert it's claim on that particular environment. This is different than a problem with litter box aversion or training issue. In these situations, the histories tend to include things like:
1.) There was a recent change to the litter box, litter location, or litter type
2.) There was a traumatic experience when our pet was using the litter box before (loud noise, attacked by another pet, etc)
3.) The litter box is dirty or perceived dirty by the pet (there are not enough litter boxes for the number of cats in the house. We typically recommend one more box than the number of cats that you have)
4.) The cat isn't using the litter box for both urination and defecation
5.) The litter box is covered or in a high traffic area of the house
6.) There is a new pet or another pet or person (small child) bothering the pet when they are trying to go
Depending on which problem is determined most likely, we can then determine a treatment plan. For territorial issues there are a number of medications that can be tried to help with the problem. Most of the medications tend to run in the anti-anxiety family and can include amitriptyline, fluoxetine, or buspar. There are also pheromone treatment options that can sometimes work (Feliway).
Urinating outside the box can be a very frustrating issue for both clients and veterinarians. The important thing to remember is that many times the answer is not straight forward and trying different treatments/solutions may be needed. Give it time and hopefully the problem will be solved.