Would an upper gi endoscopy reveal celiac disease?

Yes: A small intestine biopsy, done by upper endoscopy going down through the mouth, can reveal a diagnosis of celiac disease, especially if the patient has symptoms and blood test results suggesting celiac disease.

Yes and no: Need symptoms blood tests and small bowel biopsies, x-rays.

Depends: A person would need to be consuming at least some gluten on a daily basis for 3 weeks prior to the studies for a biopsy to obtain tissue consistent with the diagnosis. That could be as little as a slice of wheat bread/day, but someone who has been avoiding gluten can make the study less accurate. Just looking (endoscopy) is not diagnostic.