The increased permeability of the gastrointestinal mucosa is mostly seen in gastric and colon cancers due to necrosis and shedding of cancerous tissues, resulting in increased permeability of the corresponding gastrointestinal mucosa and loss of plasma proteins through leakage from the gastrointestinal tract. 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. Diagnosis of increased permeability of gastrointestinal mucosa: The diagnosis of protein-losing gastrointestinal disease can be confirmed by radionuclide-labeled macromolecule excretion test, or α1-antitrypsin test. Protein-losing gastrointestinal disease is mostly seen in gastric and colon cancers. The increased permeability of the corresponding gastrointestinal mucosa caused by the necrosis and shedding of cancerous tissues results in the loss of a large amount of plasma protein by leakage from the gastrointestinal tract. The cancer tumor compresses and blocks the lymphatic vessels, causing obstruction of gastrointestinal lymphatic reflux, lymphatic vessel stasis and rupture, resulting in large amount of protein loss. The main clinical manifestations are hypoproteinemia and edema. Small intestinal villous atrophy can be seen in colon cancer and rectal cancer, mainly manifested as diarrhea. Diarrhea, water loss and shock are mainly seen in colonic villous adenoma and occasionally in tumors of the APUD system of the gastrointestinal tract, such as VIP tumor, gastrinoma and pancreatic polypeptide tumor. It manifests as secretory diarrhea, which can lead to water loss, electrolyte disturbance, and even shock. Treatment is mainly resection of the primary carcinoma, but growth inhibitor analogs such as octreotide can also be applied, which is effective in controlling diarrhea.