The small intestine is part of the digestive system, it connects the stomach and large intestine. Anatomically, the small intestine is divided into three parts: the duodenum, the jejunum, and the ileum. The jejunum helps to digest more food from the stomach down, and at the same time absorb nutrients from the food.

There have been studies that show evidence that Crohn's disease runs in families, with about 15% of patients having a close relative with the disease.

Crohn's disease is a chronic inflammatory bowel disease with symptoms such as abdominal pain, severe diarrhea, fatigue, weight loss, and malnutrition. Based on the effect on different areas of the gastrointestinal tract, Crohn's diseases can be classified into 5 types.