The reasons for diarrhea in advanced cancer patients, which is clinically known as diarrhea, mainly include the following: Firstly, patients with advanced cancer are physically exhausted and their gastrointestinal tract digestive function is severely damaged, so even if they do not eat, they will have diarrhea. Secondly, diarrhea itself is also a common late stage symptom of gastrointestinal cancer, such as stomach cancer, pancreatic cancer, liver cancer, etc. The main reason is also because of gastrointestinal digestive dysfunction. Thirdly, advanced cancer patients are physically depleted and have low resistance, and are highly susceptible to various infections, gastrointestinal bacterial, fungal and viral infections, which may lead to severe diarrhea and become one of the main causes of death of patients. Fourth, treatment-related side effects. Although patients with advanced cancer have lost the chance of cure, palliative treatment can still prolong life, and certain chemotherapy drugs or treatments, such as radiotherapy, may lead to related enteritis and cause diarrhea.