The duodenum is located between the stomach and the jejunum. The duodenum is located in the right abdomen of the human body behind the peritoneum, the total length of about 20-25cm, it is the small intestine in the largest diameter, the location of the deepest part, the position is very fixed. The structure of the duodenum can be divided into four segments: the upper duodenum, the descending duodenum, the horizontal duodenum and the ascending duodenum. The upper duodenum is connected to the stomach to receive gastric juices, the horizontal duodenum wraps around the head of the pancreas to receive pancreatic juices and bile, and the ascending duodenum is connected to the jejunum, which makes the duodenum very powerful in digestion. When a patient develops duodenal lesions, abdominal pain or flatulence, nausea and vomiting will occur. He should go to the hospital immediately for examination and find out the cause with the help of the doctor for targeted treatment.