Thank you Theresa,
First, I am quite concerned if Smurf has had weight loss, increased thirst, and yet is losing weight. The reason is because these signs are not uncommon in elderly cats. We can see older cats start struggle to keep weight on despite a good appetite for a range of reasons. All of which can also increase their thirst (and urination) to the point of excessive. Issues that can manifest this way at her age will include conditions like hyperthyroidism, diabetes, liver disease, and kidney troubles. As well, while it isn't nice to think about, we must keep in mind that cancer in cats her age can manifest as weight loss with little other signs (just as it doesn't impinge on the body, only to steal nutrients from her).
In regards ***** ***** for her signs, it would be ideal to have her checked by her vet at this stage (if she is due for a vaccination soon, you could move it up a wee bit early and have her checked out at that time). The vet will be able to have a feel of her and just make sure there are no sinister lumps and bumps to blame for these signs. If she is clear of obvious masses, then you may want your vet to check a blood sample to assess her organ health, thyroid levels, and rule out the above issues. And at the same time, we'd want them to check her mouth since drooling can be related to nausea (which could be seen with the above but usually causes appetite loss) but more commonly is related to dental disease, oral ulcers (a concern with kidney disease), or potentially due to a growth in the mouth as well. So, we'd need to check for that too.
Alternatively, if you want to take things a bit slower or aren't keen to see the vet right away, you can consider first submitting a urine sample to your vet. Often we can obtain a ‘donation’ if the kitty is left overnight in a non-carpeted room with an empty litter box. The vet will be able to analyze it and determine if there is anything abnormal. They will be able to appreciate changes to the urine's white blood cell content (a marker of infection and common with diabetes), the presence of glucose/ketones (markers of diabetes) and bilirubin (a sign of liver disease). Furthermore, the vet will be able to check the urine's specific gravity, which tells us if the kidneys are concentrating the urine properly (since dilute urine is seen with kidney disease). Overall, this is quite a cheap and non-invasive means of checking if there are any of the these differentials could be affecting her. Depending on what is found, this can tell you if one of these issues are affecting her or whether we can rule them out right off the bat. (Though do note that with hyperthyroidism, we can only test via blood sample since the hormone doesn't enter the urine).
Finally, since there is an ongoing issue stealing nutrition from her I would note that you can try to keep her nutrition up by using a nutrient dense diet. Examples include Hill's A/D (LINK), Royal Canin Recovery (LINK), or Clinicare Canine/Feline Liquid Diet (LINK). All of these are critical care diets that are calorically dense, so a little goes a long way nutrition-wise. As well, kitten food will be more nutrient dense and could be offered as well. So, while these won't address the problem itself, it can help you slow her weight loss until you can pinpoint and tackle that cause.
Overall, I am quite concerned about Smurf. We do have a range of differentials that could cause these signs at her age. Therefore, it would be prudent to have her checked and at least have a urine sample (or blood sample) tested. Because if you are able to identify which of these issues are triggering her signs sooner rather then later, it will give you the best chance to address it, treat it as effectively as possible, and get some weight back on her.
I hope this information is helpful.
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All the best,
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