Patient: The doctor said I have ileal Crohn’s disease, what does this mean? Chen Yan, Department of Gastroenterology, Second Affiliated Hospital of Zhejiang University School of Medicine: You ask a good question, every patient should understand his or her disease, and answering your question requires a brief introduction to the anatomy of the digestive tract. Although the GI tract is an important part of our body, most people are not familiar with it, so let’s understand it briefly so we can better understand your disease (especially in Crohn’s disease, you must briefly understand the composition of the GI tract if you want to understand it). The digestive tract begins in the mouth, followed by a curved passage several meters long, and ends in the rectum. In between are a number of organs that play a role in the digestion and transport of food. First is the esophagus, which is a narrow tube connecting the mouth and the stomach, followed by the stomach, then the small intestine, the colon and the rectum. The colon surrounds the small intestine, which is further divided into four major parts: the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The small intestine can be divided into three parts: duodenum, jejunum and ileum. The appendix is located in the lower right part of the abdomen, between the cecum and the ileum, and is a long, thin, curved, blind tube. Because the appendix is very close to the end of the ileum, which is the most frequent site of Crohn’s disease, this leads to some patients being misdiagnosed with appendicitis.