Which part of the GI tract is primarily affected by Crohn disease?

Crohn's disease is a form of inflammatory bowel disease (IBD) that can affect any part of the gastrointestinal (GI) tract, from the mouth to the anus; however, it predominantly impacts the small intestine and large intestine. The most commonly affected region is the terminal ileum, which is the last part of the small intestine before it joins the large intestine. This is significant because inflammation in this area can lead to various complications and symptoms associated with Crohn's disease.

The involvement of both the small intestine and the large intestine is critical to understanding the disease's pathology. Symptoms can include abdominal pain, diarrhea, weight loss, and malnutrition, arising from the inflammation and damage to the intestinal lining. This dual involvement distinguishes Crohn's disease from ulcerative colitis, which primarily affects the colon.

While other options mention specific parts of the GI tract, they do not encompass the full spectrum of Crohn's disease, which must be recognized as a condition that can affect multiple areas, with the small intestine and large intestine being the most commonly impacted regions in clinical practice.