The increased permeability of gastrointestinal mucosa is mostly seen in gastric cancer and colon cancer due to necrosis and shedding of cancerous tissues, resulting in increased permeability of the corresponding gastrointestinal mucosa and loss of plasma proteins by leakage from the gastrointestinal tract. Gastric cancer is also a common cancer in our life and the mortality rate is relatively high, and it is caused by improper diet or viral infection, for example, some people like to eat raw food and there are more bacteria and viruses in it, or people who have irregular diet and often skip breakfast have a higher chance of getting sick, so it is necessary to understand the cause and treat it early. What is the examination? 1, chemical experimental examination: through radionuclide labeling macromolecule material digestive tract excretion test, or α1-antitrypsin detection can confirm the diagnosis of protein loss gastrointestinal disease. 2, colonoscopy: colonoscopy has important diagnostic value for terminal ileal lesions, such as intestinal tuberculosis, Crohn’s disease, other ulcerative lesions and large intestinal lesions, such as ulcerative colitis, colon and rectal polyps and carcinomas. Normal gastric mucosal epithelial cells are differentiated from primitive new cells (stem cells), which are controlled by the body when to grow and when to die, and will not grow wildly out of control. Stem cells have various proto-oncogenes and oncogenes. In most cases, the characteristics of proto-oncogenes are not expressed and no carcinogenic substances are formed, so they cannot develop into cancer cells.