Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help your neighbor with Smudge today.
Thank you for the thorough history about Smudge, it does allow us to rule some causes for her lapse in litterbox manners right off the bat. If there have been no changes to the box set-up, then we can assume that her behavior isn't due to a primary litterbox aversion. Furthermore, if she is totally indoors and cannot detect (by sight or smell) any cats outside that may be encroaching on her territory, territorial 'claiming' is likely not the culprit for her signs either.
That said, we do have to consider that since the urination issue is intermittent and the fecal issue is more common, that we could be facing two separate triggers for her signs (since there is no rule that only one thing can be amiss with elderly kitties). And with this weight loss, I would be a wee bit concerned that at least the intermittent inappropriate urination may be a secondary sign of an ongoing geriatric health issue (ie kidney disease, liver troubles, diabetes, hyperthyroidism, etc). This is because often we will see signs like weight loss (despite a good appetite), increased thirst and urination arise due to these conditions. And as a cat has to urinate more due to the health issue, we can see onset of this type of behavior. Therefore, your neighbor may want to consider just submitting a urine sample (often we can obtain a ‘donation’ if the kitty is left overnight in a non-carpeted room with an empty litterbox) to the vets. This can be tested in-house (which is quite economical to do) and the vet will be able to analyze it and determine if there is anything abnormal. They will be able to check for bacteria and white blood cells present (signs of infection, often secondary to urinary dilution caused by these conditions), and rule out other issues like crystals, bilirubin (a hint of liver troubles), and ketones/glucose (a marker of diabetes). They can also check the specific gravity of the urine, which will just give them an idea if the kidneys are working as they should. If these are all found to be normal and her signs are settling with the aforementioned home management, then it may be that this was a stress induced behavior (of which the treatment you listed would be appropriate)
Otherwise, we have to consider the fecal issue. Now we do see many older cats start defecating outside the box at older age due to arthritis getting to be too much for them. The reason is because fundamentally cats, unlike dogs, go to great lengths to modify their lives around avoiding things that cause them discomfort. This means that when a cat has arthritis, they will take steps to modify their lives and just decrease doing the things that are causing the pain. (where dogs just keep using sore joints until they are lame). It is wise for the cat, harder for owners to pick up when there is a problem. And of course not ideal when the situation making them sore (that they then go to avoid) is using the litter box.
Now in cats with underlying arthritis, litter box disuse is the first sign we see that there is a problem at all. The reason is because no matter how much discomfort it can cause, life demands that a cat not stop using the toilet. That said, cat do take steps to deal with this (not always successfully). These affected cats will tend to be more likely to ‘hold’ feces for longer then they might have before. And because of this, we may see sometimes see harder feces being produced, which in turn are more of a strain to pass. Furthermore, since passing feces requires significant forces on the body and going in the box means doing this while standing on two feet balancing on pebble like litter; these cats often won't want to put themselves through this. Therefore, often in cats with back pain or arthritis (typically of the hips/back/hind legs), this can be a bit much. And this is when they just decide that it is easier to go outside the box (often choosing a substrate that they can get better grip on like carpets or hard floors are free of the pebble like texture that litter has). For some cats this will then become an all the time occurrence, while others will just do it intermittently (when they can't be asked to deal with the box). The problem is the more they do it, the more likely they are to continue to do so as it goes from being a lapse to a habit
Therefore, because Smudge is older and this is likely playing a role here, your neighbor may want to ring her vet and see if they'd consider a trial for her on a cat-friendly anti-inflammatory (even just a small dose to see if this helps) like Metacam. Alternatively, they may consider trying glucosamine/chondroitin supplementation with your cat. This is a nutrient supplement that is available at your vets, pet shops, and health food stores (as capsules, liquids, and even treats). It works by aiding joint suppleness by helping cartilage replenish itself and blocking enzyme destruction of cartilage in the joint. Often we can find this helpful in animals with mild signs, but it might be enough to take some of the discomfort away from her and help her to comfortably use the litter box. Normally we give kitties 50mg glucosamine + 15mg chondroitin a day per 10 pounds of body weight. So, do consider trying this with her.
In the meantime, your neighbor may want to consider trying a litter box that has a lower lip, so that she has no excuse/difficulty getting into the box. As well, they could also consider changing her litter to a paper or sand based litter to see if this just takes some of the strain of litter box time. And of course, if you are concerned that she is 'forgetting' where her box is, they can try a litter attractant as a reminder. As well, you had the right idea with putting a box in the other places she had be going.
Finally, you noted they are using a discouraging spray but didn't note what kind. Therefore, I do just want to say that they do need to make sure that this cleaner/spray is one that is an enzymatic odor neutralizing cleaner (LINK1 LINK 2). This is because normal cleaners will eliminate the smell to us but not necessarily to her delicate nose. And if she may still be able to smell her own scent, then she may choose to go there again. Your neighbor can detect any other sites she may have urinated on using a black light.
Overall, defecating out of the box is not something cats do lightly. It is a behavior that is actually going against her instincts. Therefore, we have to take this as a sign that something is amiss and her age, lack of historical behavior triggers, and her ability to mostly continue to urinate in the box makes arthritis is a prime suspicion for her. So, for the fecal situation, I would advise trying the above. In regards to the urine situation, it does sound like it is perhaps settling but if it is not then it would be prudent to check a urine sample to make sure those signs are a hint of a health issue like kidney disease.
I hope this information is helpful.
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