Which section of the intestine is most commonly affected by Crohn's disease?

The ileum is the section of the intestine most commonly affected by Crohn's disease. This inflammatory bowel disease can involve any part of the gastrointestinal tract, but it most frequently affects the terminal ileum, which is the last part of the small intestine before it connects to the large intestine. Involvement of the ileum can lead to specific symptoms such as abdominal pain, diarrhea, and malabsorption of nutrients, particularly vitamin B12 and bile salts, highlighting the essential functions of this area in digestion and absorption.

The terminal ileum's structure and its role in the immune response are significant factors contributing to its susceptibility in Crohn's disease. The inflammation that occurs can cause changes in bowel function and potentially lead to complications such as strictures or fistulas.

While Crohn’s disease can also affect other parts of the intestine, such as the colon and parts of the small intestine like the duodenum and jejunum, these areas are less frequently impacted compared to the ileum. Thus, identifying the ileum as the most commonly affected site provides critical insight into the disease's pathology and management.