Carcinoid syndrome refers to the development of carcinoid tumors in any part of the digestive tract except the esophagus, which is located in the appendix in 1/3 of cases, mostly in females, and rarely metastasizes. Those located in the stomach account for 2%, and the rest are located in the duodenum, colon (most common in males), gallbladder and Meckel’s diverticulum, etc. They can also occur in the bronchial tubes and the ovaries, but they are less common. Those occurring in the small intestine are highly malignant and may metastasize to the lungs, bones, and other intra-abdominal organs. Bronchial carcinoid tumors associated with carcinoid syndrome have a poor prognosis. Carcinoid tumors can occur at any age. 1, 24-hour urinary 5-hydroxyindoleacetic acid is more than 30mg.In the carcinoid cells of stomach, the lack of dehydroxylase enzyme leads to the low concentration of 5-hydroxytryptamine in the blood, while the concentration of 5-hydroxytryptophan acid is increased.The amount of urinary 5-hydroxyindoleacetic acid in 24 hours fluctuates a lot, and it is affected by the food. For example, after eating potato, banana and pineapple, the amount of 5-hydroxyindoleacetic acid excreted in urine will increase, so it is necessary to repeat the urine test several times to make the diagnosis reliable. 2.In patients who are highly suspected to be carcinoid tumor and the amount of 5-hydroxyindoleacetic acid discharged in urine does not increase, stimulation test can be conducted. The test method is to use 5% dextrose 500ml intravenous drip, measure blood pressure and pulse every half a minute, but after the blood pressure and pulse are stabilized, 1μg of adrenaline can be injected intravenously, and if there is no reaction, 1μg can be added every 15 minutes until there is a reaction. However, the maximum dose should not exceed 15 μg each time, and if there is still no response with 15 μg, this test is no longer performed. Since the stimulation test can cause serious hypotension and bronchospasm, this test should be conducted with special caution. 3. Carcinoid tumor of gastrointestinal tract can be diagnosed by X-ray examination, B-mode ultrasonography and CT for those with liver metastasis. For bronchial carcinoid tumor, cancer cells can be found in sputum, and bronchoscopy and chest tomography can be performed. When carcinoid tumor occurs in the pelvis, it can be found by gynecological examination, B-mode ultrasonography and CT.