Hello & welcome. I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
I am very sorry to hear about your lass's situation.
It sounds like her vet feels that all her ongoing issues are overwhelming her and it is time to let her go. In this case, you have 2 options. First, you can agree with them and have her put to her sleep before she dehydrates, gets weaker, or suffers with this. Otherwise, you could consider having a second opinion. And if she has recovered from GI issues before, then the latter may be best. you may find it is possible that her GI signs are due to an opportunistic infection and aggressive treatment (ie IV fluids, injectable anti-nausea treatment, appetite stimulants, and stabilization of her diabetes) could be tried to see if she can recover.
Or if you didn't want to put her through invasive treatment, at the very least you could try some supportive care. For example, if her vomiting isn't profuse, you could try an oral OTC antacid like Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), or Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac). Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do check with her vet before use if she has any known health issues or is on any medications you didn’t mention. As well, if you try this and find her nausea too severe to keep it down, then that is usually a red flag that we need her vet to bypass her mouth with injectable anti-vomiting medication.
Once that has had time to absorb and she is steadier on her stomach, you can consider starting her on a light/easily digestible diet. Start with a small volume (a spoonful). Examples you can use are cooked white rice with boiled chicken, boiled white fish, cottage cheese, scrambled eggs, or meat baby food (as long as its garlic/onion free). When you offer that spoonful, give her 30 minutes to settle. If she keeps the food down, you can give a bit more and so on. As her stomach stabilizes, you can offer more. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset and reduce the diarrhea as well. You can even add fiber to this (ie canned pumpkin) to bulk her stools up.
Finally, as long as you have not seen blood in those stools, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure if the cause were infectious; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options for your wee one, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p). This is available OTC at most pharmacies. Otherwise, Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (which is available OTC at vets, pet stores, and even Amazon) would be another option. All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria. So, these can be used as a short-term means of soothing this upset GI.
Overall, without testing to determine the cause of her newest signs we cannot say they are untreatable, but with everything she has ongoing they may be difficult to settle. And this is likely what her vet is thinking. So, you could try her with the above options to try to soothe her signs +/- have a second opinion from a different local vet. Otherwise, we don't want her starving and wasting away at home and may need to consider letting her go.
Please take care,
If you have any other questions, please ask me – I’ll be happy to respond. **Afterwards, I would be grateful if you would rate my service by clicking on the "Rate my Expert' button at the top of the page as this is the only way I am credited for helping you. Thank you for your feedback!