My Chihuahua normally has a voracious appetite and will eat anything. She came to me with my fiance about a year ago. She's 7 years old and intact. Until she came to stay with me she was very overweight. She's now at an ideal weight. Or would be, if she would firckin' eat. About a month ago she refused food for a day or so, coupled with some diarrhea with traces of blood in it. Her poops are normally well formed and regular, and her appetite never wanes. I brought her to the vet. He checked her blood and stool, gave her an ultrasound checking for pyo and abdominal masses, etc and checked her teeth. Ultimately he didn't find anything. She started eating again shortly after the vet visit. Since then she's stopped eating half a dozen times or so, but not always coupled with diarrhea. Between hunger strikes she acts normally and is bright and playful. Right now we're in one of the worst bouts of it and she's not eating much at all, and her poos are liquid and with some blood in them. I've brought her back to the vet once more where he gave her another ultrasound and checked her teeth more thoroughly but again could come up with no answer for her condition. Because she's a tiny dog and she's been slimmed down so much, she can't exactly afford to lose any more weight. She gets sickly looking pretty fast. My fiance has requested we pile some more weight on her to act as a buffer, but her refusing food is a symptom, so fattening her up doesn't feel like an answer. Plus she has a luxating patella - I want to keep unnecessary weight off. She's also had back/pain problems in the past. She eats 6-Fish Orijen. Anyways, does anyone have any thoughts on what could possibly be the issue? And does anyone have any thoughts on what my next step should be?