vomiting and runny poo poo's

Kitty is 4 years old and has puked for as long as I can remember. I have tried all of the foods: Science Diet hairball, sensitive stomache, and now the d/d duck both dry and canned. I have also tried the Nature's Choice canned foods. She also has a food allergy to some kinds of fish. I finally took her to the vet because I am finally accepting that this isn't hairballs and not normal behavior. She is now having the runnies about once a week and it seems to go along with the vomiting. Her blood work came back with an ALT of 279. The vet wants to do x-rays to look at the liver, esophagus (s.p.) and intestines. $$$ is an issue so she also suggested 1-2 weeks of oral Prednisone as an alternative. Although she doesn't feel good about doing that without knowing for sure what it is. We are considering the meds instead of the x-rays. I am worried that it won't stop at the x-rays and we really can't afford all of this right now. Any suggestions?
Thanks,
Kate

[Aleda M Cheng, D.V.M., C.V.A]

Did your vet do a thyroid test?  Other than duck have you tried any other hypoallergenic food?  Her liver enzyme ALT is already increased, prednisone may increase it even more, however in this case the prednisone would only be used for a short term and cautiously.  This type of use of prednisone is a therapeutic trial and may help diagnose the problem.  It is worth a try since you are unable to do a battery of diagnostics.  If the pred. is ineffective you can still have the X-Rays performed or go directly to an ultrasound in the future.  Although it does sound like IBD (inflammatory bowel disease).  Good Luck!