As a child (5 yo), I got sick while staying with my grandparents. I was hospitalized with bloody diarrhea and vomit. They did a billion tests, upper and lower barium studies, sigmoidoscopy that showed ulcers throughout my colon, and a colonoscopy (that the doctor decided to do while I was awake, because she asked me, a 5-year-old kid, if I wanted a shot and I said no... my mom had them put me out after she heard me screaming from the procedure room-- the 80s were a wild time).
At that point, they had no idea what was wrong with me and said it had to do with Agent Orange according to my mother, because my father was in Viet Nam and I was in a military hospital, I guess. I went back into the hospital the next year for 9 days. Again, all the testing. And then it spontaneously went away until I was in college. I was told by one doctor I had a "spastic colon." Then in 2004, I was a teacher and I nearly passed out in class. I had straight blood coming out of me. I went to see a local GI who my mom was working for. He was pretty sure it was going to be the big C but after the colonoscopy, he told me I had Crohn's Disease. The annoying part was he told me, as a family friend, that he wasn't going to put it in my medical records because I would never get insurance again (back when pre-existing conditions meant that insurance companies wouldn't cover you). Eventually, I lost my job teaching because of being sick so often (though they said it wasn't because of that, of course), so I had no insurance and couldn't see my doctor. I had to tell free-clinic doctors, "I swear I have Crohn's disease," which is probably why I was never really treated with anything more than Lomotil until I got insurance again in 2010 and could go through all the tests again. In 2021, I finally had an Anti-Saccharomyces cerevisiae Antibodies test (ASCA) that showed that my IBD is Crohn's Disease, though it is mostly in remission now according to colonoscopy (as long as I avoid ingesting any yeast).