Hi Angie,

Sorry to hear this. First, I'm not a doctor, so my suggestions are only that, suggestions. Plus, I know nothing of his age, overall health status, background, etc. He should consult with a doctor with whom he has confidence.

Now, that said, diarrhea can be caused by many things. I'd think he should have complete stool cultures done that look for bacterial infections, things like C-Difficile, H. Pylori, intestinal parasites, etc.

A colonoscopy with a small bowel follow-thru would either rule in or rule out things like Crohn's disease or Ulcerative Colitis or Diverticulitis. An endoscopy would allow them to look at the villi in his small intestine which could show if he's having a gluten problem/Celiac disease, etc. 

Those are my initial thoughts and I'm sure the doctors will have other ideas as well. The hard part is, diarrhea can be caused by many different things and they may or may not be able to come up with an answer on the first go-round. It can take some time to figure out these things so patience can be very important.

Best of luck to him,

Elizabeth