**Abstract**

Duodenal disorders are difficult to identify clinically because of the non-specific symptoms. They may or may not be identifiable through routine radiographic, ultrasonographic, or laboratory evaluation methods, because many diseases of duodenum primarily involve the mucosal surface. Duodenal ulcers, inflammatory bowel disease (IBD), and small intestinal bacterial overgrowth (SIBO) are the duodenal disorders. Duodenoscopy is an efficient way of identifying the abnormalities of mucosal irregularities, distortion, ulceration, neoplasia, and inflammation, and it is also useful for obtaining mucosal biopsy and duodenal juice for routine histopathological and bacteriological studies. This paper will provide more detail about the advanced diagnostic methods and therapeutic measures for various duodenal disorders.

**Keywords:** duodenal ulcer, IBD, SIBO, duodenoscopy, malabsorption
