Crohn's disease most often involves which parts of the digestive tract?

• A. Esophagus and stomach
• B. Ileum and colon
• C. Rectum only
• D. Duodenum

Answer: (B)

Crohn's disease most often involves the terminal ileum and the colon, together called ileocolitis. This distribution is classic for Crohn's, reflecting its tendency for segmental, transmural inflammation that frequently starts at the end of the small intestine and extends into the first part of the large intestine. While Crohn's can affect anywhere in the GI tract, involvement of the ileum and colon remains by far the most common pattern. Involvement of the upper GI tract (esophagus, stomach, duodenum) happens but is much less common, and disease limited to the rectum alone is more typical of other conditions such as ulcerative colitis. So the ileum and colon best match the usual Crohn's distribution.