How to get insurance coverage for elemental nutrition?

Hi all,
After years of crippling motility problems, I've developed some more symptoms that, together with some of my blood test results, seem suggestive of IBD, and I'm working with a new GI to find out if I have it. In the past few months, I've lost the ability to eat much solid food other than chicken, which has no fiber, because anything else gets stuck in my system behind what feels like a blockage in my right groin. I'm not sure how much longer I can keep doing this and am hoping to be able to go on the elemental diet soon - basically the oral equivalent of tube feeding - to get bowel rest and start healing my IBD, if that's what this is. However, most GIs and dietitians don't seem to have experience with patients on the elemental diet, and I'm at a loss as to how to get insurance coverage for it (I live in AZ by the way) - especially if I have to go with an OTC brand of elemental shakes, like Absorb Plus Amino orange/mango formula, which I'm currently looking at because it's the only option I've found so far that doesn't have ingredients derived from foods that I'm allergic to. It's insanely expensive, though!

Has anyone done the elemental diet before, and were you able to get insurance coverage for it? If so, what was the process like and what questions should I ask my insurance provider? Thanks in advance! This situation has me really overwhelmed.