Good morning, Kerry.
I see you have asked for a bit of UK veterinary input and as I am UK based, I'd like to add to Dr. Deb's great answer for Turvy's kidney issues.
First, I do want to note that I fully agree with Dr. Deb's thoughts on Turvy's diet. Even if a special diet is amazing for managing a kitty health condition, if they won't eat it then its unlikely to be of benefit for them. Therefore, I would suggest that it may be worth trying the Royal Canin Renal wet diets (my own kitties love them so much that the healthy cat is always stealing my own kidney cats food). But if you do and he decides that he is stubborn and not going to have the special diet in any form, then we have to find a compromise with him.
In that case, we'd want to consider any diet he will happily eat but ideally aim to use one that is as close to those lower protein, lower phosphorus, and lower sodium levels that are in the kidney diet. (So it is worth a peek at the back of all the cat food labels to compare). Furthermore, if you find a diet he likes with as low values of those components, you may want to consider offering the wet food version if possible (since its 35% water and will get more hydration into him to support the kidneys --especially as they never drink as much as they should). Again, at the end of the day, eating is most important aspect for a comfortable kitty life and after that we then want to consider how we can make what they eat best for their respective conditions.
As well, I completely agree with Deb's mention of not letting the numbers blind you. We do use those kidney values to give us an idea of how severe their kidney disease is; but just like people some animals feel worse in early stage disease as opposed to others. The numbers are just a guide to let us know how fast kidney decline may or may not be happening. But in regards XXXXX XXXXX Turvy, the key aspect to focus on is how he is. Because if he isn't eating, is depressed, lethargic and not doing the things he loves, then the mildly elevated numbers are irrelevant and we have a kitty that we want to see if we can get feeling better.
So, if you get Turvy onto a dietary compromise and he still seems lethargic and down, then its worth a word with his vet. It may be that the diet change is a red herring and Turvy is just feeling poorly even with early stage disease. In that case its worth discussing using medical management (perhaps even just a single daily treatment with Fortekor) in place if intense diet modification or even just to trial and see if it helps Turvy's kidneys filter better and therefore make him feel better. If it doesn't, then he doesn't have to stay on it at that stage. If it does, then there is no harm in giving the kidneys some medical support sooner then we'd have perhaps thought about doing so.
As well, as Deb has noted, we do see nausea associated with kidney issues. Now Pepcid is a bit difficult to find OTC here, so instead you may want to consider trying or Zantac (LINK). Otherwise, you can speak to your vet about dispensing Pepcid/Famotidine (though may practices may have to order it in) or they may be able to provide liquid Zantac (which is a bit easier to dose and administer then OTC tablets) or Cimetidine. They should be amenable to do so since they have just seen him recently.
Also, I do want to just note that kidney kitties can be prone to urinary tract infections. This is because their kidneys just cannot make urine as concentrate as it once was, therefore the diluted pH is less of a defense against bacteria. To make these situations even more of a challenge, it can be quite easy to miss urinary infections in these wee ones since their kidney condition tends to cause them to have voluminous urination (therefore we don't see the increased frequency of small volumes). Therefore, if he is a bit down with a non-specific lethargy, you might want to just have a urine sample checked. Urine samples can often be collected by leaving the cat in a non-carpeted room with an empty litterbox overnight. Otherwise, if time is of the essence and he has a full bladder on examination, then vet can take a sample directly from the bladder for testing (+/- culture). Often the treatment approach in these cases is just the same for any cat with a bladder infection, its just that we have to be more vigilant in picking up when they may have one.
In regards XXXXX XXXXX product that Deb mentioned, I see it on our Amazon but it doesn't appear to be in stock. I can see the benefit of the product for Turvy's situation but must note that it isn't something we really have over here or regularly use. Instead, we still tend to use the Omega 3 fish oils for their anti-inflammatory properties and support the old fashioned way (with a trip to Hollands & Barrett). Typically we will give kitties a daily dosage of the Omega-3's DHA/EPA at a rate between 300-500 mg combined each day.
Finally, I did just want to give you a few links to help you get an idea of the treatment approach we take with kidney disease in our kitties. First, the FAB (now known as International Cat Care) has a good link on treatment overview (here). As well, since Deb mentioned giving subcutaneous fluids (something to speak to your vet about), I wanted to give you a wee overview of that as well (which you can find HERE).
I hope this information is helpful.
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