Let's say we surgically made a bypass that goes from the bladder to the large intestine, don't ask me why we would do that. How would you call it? A "bladder-large-intestine" bypass? I have no idea how we refer to a thing like that. It seems we would use a phrase instead of a term. How would you do it?
It seems to me that such a thing could be called an "artificial duct." See this definition of duct: https://www.merriam-webster.com/dictionary/duct. But see my comment also.
Well, there the term fistula.
Fistulas occur abnormally but naturally and can cause all sorts of problems, depending on the organs involved, but they can also be created deliberately for therapeutic reasons. A fistula is an abnormal connection between two organs or blood vessels, and the term can apply to intestines or any "hollow organ". These are created between arteries and veins, usually, but the basic concept could be applied to any appropriate pair of organs or vessels.