An endoduodenal fistula is a pathological channel formed between the duodenum and other cavernous organs in the abdominal cavity, with openings in the duodenum and the corresponding cavernous organs, respectively. A duodenal fistula that communicates with only one organ is called a “simple duodenal fistula”, while a fistula that communicates with two or more organs is called a “complex duodenal fistula”. The former is clinically common, while the latter is less common. In endoduodenal fistulas, the contents of the duodenum and the corresponding cavernous organs can communicate with each other through this abnormal channel, resulting in a series of changes such as infection, bleeding, loss of fluids (diarrhea, vomiting), water-electrolyte disturbances, impaired organ function, and malnutrition. Symptomatic fistulas should be treated with aggressive surgery.