A gastroscopy is done to be able to examine the esophagus. During a gastroscopy, the patient is lying on the left side. The doctor puts the gastroscope through the mouth, then passes through the pharynx to reach the esophagus and stomach, and finally observes the duodenal descent and duodenal papilla. Therefore, gastroscopy can observe the specific conditions of the esophagus, stomach and duodenal mucosa at the same time. For example, common clinical diseases such as reflux esophagitis and esophageal cancer can be observed through gastroscopy. In addition, in the process of gastroscopy, the esophageal lesion site can also be sampled, which helps to further clarify the nature of the lesion. The specific examination method should be taken into consideration of the individual’s specific situation and be guided by the doctor’s arrangement. If you need to have a gastroscopy, make sure to prepare in advance by fasting for more than 8 hours.