The diameter of the duodenal bulb is about 4 to 5 centimeters. The duodenum is the part between the pylorus and the jejunum is the thickest small intestine and is divided into four parts including the duodenal bulb, the descending duodenum, the horizontal duodenum and the ascending duodenum. The duodenal bulb is approximately 4-5 centimeters thick. The duodenum is the deepest and most fixed small intestine, the pancreatic duct and the common bile duct both open into the duodenum, so the duodenum receives both gastric juice and bile injection, and is clinically susceptible to peptic ulcers, which can be initially determined by gastroscopy. If you need to detect duodenal lesions, it is recommended that you consult the gastroenterology department of a regular hospital for gastroscopy.