Colonoscopy can not see the duodenum, colonoscopy refers to the colonoscopy, and small intestine microscopy, more often done is the colonoscopy, mainly to see the large intestine, small intestine microscopy, as the name implies, is to see the small intestine. To understand the lesions of the duodenum need to do electronic gastroscopy, electronic gastroscopy is accurately called fiberoptic gastroduodenoscopy, can be seen from the entrance of the esophagus to the descending section of the duodenum, to understand whether there are lesions in the upper gastrointestinal tract, when necessary, you can also perform electronic gastroscopy to take a biopsy, microscopic treatment, etc. A common lesion in the duodenum is duodenal ulcer, especially bulbous ulcers are more frequent. If a patient clearly has a duodenal ulcer, he or she needs to cooperate with a specialist to give regular anti-ulcer treatment to avoid complications such as bleeding and perforation.