First, I have to say that I am quite concerned about your lass.
Now your history is thorough and it does let us start to rule out some concerns but it does raise some further concerns as well. Of course, we do have to consider whether this vomiting is a side effect of the issue causing her current weight loss or an opportunistic infection taking advantage of her weakened state.
With that in mind, to start, I'd note that we can try to reduce has nausea and this vomiting as we narrow down the causes for her lost weight. To do so, you can try her on an OTC antacid like Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), or Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet) 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 Afterwards, a light diet (ie rice with boiled chicken, scrambled egg/white fish/or cottage cheese could be offered to offset her stomach upset).
Otherwise, we need to focus on her weight loss. Now when we have an dog losing weight, we do have a range of issues to consider. We can divide into 3 categories: (1) conditions that cause weight loss due to decreased nutrition intake (a concern if she is eating less), (2) those due to increased output (less likely if she isn't having diarrhoea but we cannot rule out kidney/urinary based protein loss), and (3) those internal issues that cause weight loss by siphoning nutrition away from the body (ie worms, metabolic diseases like diabetes, organ issues like liver or kidney, cancer, etc). So, in her case, we would have to consider whether weight is being lost due to her appetite issues (where nausea and discomfort due to oral disease would be our top suspect) or related to an internal issue stealing from her.
In regards ***** ***** to the bottom if her signs, to start if you haven't already, you should consider worming her. Severe worm burdens can cause GI upset, loose stools, increased appetite, and weight loss. Now there are a range of worming products available over the counter but you want to use a good quality wormer. In this situation, it would be ideal for you to treat her with Drontal, Panacur, or Milbemax as they will cover all the worms in question. Do make sure to have an idea of her weight before purchase wormer to make sure you get the correct dose for her size.
Further to worming, it would be ideal to have her checked by her vet (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 just make sure there are no sinister lumps and bumps to blame for her weight loss. If you were able to bring in a urine sample at that point, the vet could check it for signs of diabetes (ie. sugar in the urine) as well as check its specific gravity (how concentrated it is) that can tell us if there are problems with her kidneys. Depending on their exam findings, you may also want them to check a blood sample as this will let you appreciate the function of all her organs and how severe any may be affected.
Finally, once we have her stomach more settled we can consider starting her on a calorie rich diet like Hills A/D, Royal Canin Recovery diet, or even canned puppy food. As well, we can also supplement with a liquid diet (ie Clinicare, Dogsure) or paste supplements (ie Nutrical) These will all get more in per bite even if we cannot get much in and slow her weight loss.
Overall, in situations like this we can see weight loss in elderly dogs due to a range of issues. With your history, we are able to rule out some concerns. Though with those related to appetite loss and aforementioned internal conditions that siphon nutrition, we need to tread with care. Therefore, in this case, it would be ideal to at least have a urine sample checked at this stage but do consider having a check up +/- blood sample tested with her vet to identify which of the above is to blame at this stage. That way you can address this early and help keep her from wasting away before your eyes.
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!: )