Leaky Gut is not a fully recognized medical syndrome. The simplest of searches on google point to it's wiki, and a response from
England's NHS. Here in the states, I would assume coders would try to use K59.9, which does not identify as Leaky Gut Syndrome, to get insurance companies to cover charges.
I feel like you're getting swept up with big words. Science doesn't scream "BUT CAN YOU DENY THIS!!!?1". Science demands observable, quantifiable results, with models run through clinical trials. What's being described here, is a theoretical process that makes the most sense to him.
Four years ago, sepsis management was antibiotics and no fluids. After putting it in practice, the absence was questioned, and then changed to "Yes, Fluids!", as we got more data. Last year, it changed again to ok, some fluids, but let's help the patient process them to prevent edema, kidney failure, etc. You can see that written out for ICU patients
here.
We had, what we thought was an understanding. That understanding, after observed more acutely, changed. We thought we had another understanding. After observing that, it changed. We're now attempting to find the optimal rate, and I have no doubt that when it's all finished will become a scaled chart of finding the best rate for the patient.
Science doesn't ask "Can you deny this". Science asks "Can you prove this".