[Chenza]

I am in need of some suggestions. My little Rigby is 4 yo unspayed female. For the last at least 6 months, she has not been acting right. Depressed and not eating great. First I thought her teath hurt so I had them cleaned and she was on antibiotics. Slight improvement, but symptoms returned. She has been worked up for liver shunt, (negative) and thyroid. CBC and Chem and Urinalysis were all normal. (Slightly high T4) She saw both my vet and had a consult with internal medicine specialist at a Specialty Hospital. My vet thinks it chronic pancreatitis, and she seemed somewhat better on boiled chicken, sweet potatoes and string beans which I was cooking. She would eat, but stop abruptly and walk away and usually burp loud, then resume eating. She seemed to be in pain after she ate. Then she started itching and threw up fer food a couple of times, so we suspected allergies and switched to fish and rice. This was ok, but I worried about a balanced diet, so I started looking for a low fat dry dog food. I tried Nutro CHicken low fat (9gms) and she was doing great until she started itching again. I bought Blue limited ingredeient turkey, itching resumed, so we switched to salmon and sweet potatoe. 12 gms of fat which my vet said is the max. She has done a dive backwards since on the blue buffalo, and has started acting like she is in pain after she eats again. She ate some baby food tonight, and started shaking and couldn't get comfortable. Her abdomen was tight like she had gas, she burped a few times, and it past. She is better now, but will happen again when she needs to eat. No vomiting and pee and poop are completely normal.
Im stupmed, and so are the 2 vets. Could be chronic pancreatitis flared from the 12 gms of fat in the Blue Buffalo. Any suggestions, ideas about meds for gas like Mianta. I'm calling the vet in the morning, but always get great suggestions from others who have yorkies. Also, any suggestions for a low fat dog food that is not chicken based?
Thanks in advance for your suggestions.