Just seeing this thread after responding to your PM. I hope some of what I said will help.
As Wylie's Mom said ideally it is good to know the cause of the PLE but IF a person cannot afford scoping and/or if the pup is too ill for a scope, it can be treated! In yorkies, most of the time it is lymphangectasia. My Cookie had lymphangectasia and IBD. We had a YTer years ago who had a pup with an intestinal fungal infection. That would probably be unlikely in NYC as it comes from soil and usually is found in the Southwest. I like the following link for information:
Protein-Losing Enteropathy (PLE) in Dogs
In reading this thread I see your parents have been to a few vets....tell them to STOP that because it will cost more money in the long run. A specialist is not cheap, but they are SO much more familiar with this illness unless you find a really well informed vet. The specialists are more likely to know new treatments as well as just seeing more of it and knowing more about how to treat it. They can find one at:
American College of Veterinary Internal Medicine > Home There is a search engine to find a specialist closest to them. Tell them to look for Internal Medicine ... for Small Animals Up front, the initial exam is usually around $150 .. they will need to have their vet refer them and send all of her records.
--------------------- below is my message I sent in response to your PM which kind of covers basics....
I am so sorry to hear this. I always hate when I hear of a PLE dog that isn't responding to treatments. It is not curable, but is treatable and can be managed in some cases. My Cookie lived with it for years before ending up getting lymphoma which is what took her.
Is a specialist weighing in on her treatment? They could possibly have some ideas beyond what she is being treated with.
Diet is ultra important (low fat)....and yes, getting them to eat is always a huge challenge. Have they tried any appetite stimulants? I have always used Mirtazapine but there is another med being used now called Entyce. Vets are happy with the results! My DIL's dog was recently in ICU with liver issues and they put her on it and she did start eating. She had not eaten for four days and they were discussing a feeding tube prior to putting her on the meds and she ate.
If she is filling up with fluid, I imagine her albumin and protein levels must be very low. I have seen plasma turn that around....has that been tried?
If your parents can, it might be wise to get her into an internal med specialist and even perhaps hospitalize her for intensive treatment.
Hope this helps a bit. Feel free to message me any time.