Which diagnostic finding is referred to as the "string sign" on a barium enema?

The "string sign" is a specific diagnostic finding associated with Crohn's disease, particularly when it affects the ileum (the last part of the small intestine). This sign is visualized during a barium enema exam, where barium is introduced into the colon to highlight areas more clearly on X-ray images. The string sign appears as a narrow channel of barium that outlines a stricture or narrowing in the intestinal lumen, which is characteristic of the inflammation and scarring that occurs in Crohn's disease.

Crohn's disease can cause segments of the bowel to become narrowed due to transmural inflammation, leading to this distinct appearance. This is in contrast to other conditions like ulcerative colitis, which typically presents with continuous inflammation of the colon without strictures, or colorectal cancer, which would show a mass rather than a string-like appearance. Functional dyspepsia is not related to structural changes in the bowel and thus would not be associated with the string sign seen on a barium enema.