I recently came online and see that your question about Suki hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
Inappropriate urination issues can be extremely frustrating for both owner and vet alike.
They are going to be either secondary to a medical issue (lower urinary tract infection, bladder stones or Idiopathic which means we can't find an underlying cause) or behavioral.
If an underlying medical issue has been ruled out (urinalysis, culture and sensitivity, x-rays and/or ultrasound have been done), then you're left with a behavioral explanation for this behavior.
I'm assume for the sake of argument that her inappropriate urination is behavioral since she chooses to urinate in the same spot rather than all over the house but if at least a urinalysis hasn't been done, I'd suggest one just to confirm that it's clean.
As to what would trigger or cause this inappropriate behavior, well, that's sometimes a more difficult question to answer.
Cats can use urination (and sometimes defecation) as a means of communication with other cats and with humans; they are basically staking a territorial claim with their bodily fluids, Psychological stress, such as the presence of other cats, prolonged absence of the owner (who is usually viewed as a parent by the pet cat), or other problems may create a need for a cat to reassert a territorial claim. Other cats will behave this way because there is either something about the texture of the litter they don't like, the smell of the litter is objectionable, or they might have experienced pain/discomfort while urinating in the box and now want to avoid it.
Since litterbox issues are often the trigger for inappropriate urination problems , I'll summarize the results of studies done on litterbox preferences just to cover all the bases"
1. Some cats really like a very clean box; when it becomes dirtier than they prefer, they'll urinate elsewhere. So, the box should be scooped at least daily or twice daily and the entire box cleaned weekly with soap and water; avoid harsh smelling chemicals.
2. The number of boxes and size is important: The rule of thumb is one box/cat plus one box. A litter box length should be at least one and a half times the length of the cat (not including the tail) so they have adequate space to maneuver and cover their waste.
3. Cats prefer clumping litter. 4. Cats prefer unscented litter. 5. Cats don't like hoods on their boxes because they retain odors.
6. Cats don't like their boxes where there's a of noise or foot traffic; they prefer privacy. 7. Use of enzymatic cleaners to degrade the fecal material rather than just cover up the odor (the cats can still detect it) are preferred. If Suki urinates in one particular area more frequently , she may think that it's ok to do so snce the urine odor may linger.Other helpful hints in addition to the above:
1. Use of Cat Attract in the litter
2. Sometimes confinement in a smaller room/space with food/water and the litter to "retrain" them can be useful.
3. If you think that stress may be a factor, use of Feliway diffusers or a spray (which are natural pheromones) may be of benefit since these products are intended to reduce anxiety. These products are available on the internet or at most pet stores.
I'm not familar with Serene UM calm drops although I suspect this may be something similar to Feliway but just an oral version. It might be worth it to try Feliway as well.
When all else fails and this is strictly behavioral in nature, I have treated these cats with drugs such as Prozac or Xanax which can be quite effective in the vast majority of cats with inappropriate urination issues. This may not be something that you'd want to consider right now, but at least you have the option.
I hope this helps but, againb, my profuse apologies for the delayed reply. Deb