Strongly positive fecal occult blood may be caused by gastrointestinal bleeding due to inflammation of the upper, middle and lower gastrointestinal tracts, tumors, vascular diseases and systemic diseases. When the amount of gastrointestinal bleeding is small, usually within 5~10ml, the feces may have no color change visible to the naked eye, but a small amount of red blood cells can be detected in the occult blood test, i.e. occult blood positive. 1. Lower gastrointestinal diseases: mainly including colon diseases such as acute bacillary dysentery, ulcerative colitis, colon polyps, colon cancer; rectal lesions such as rectal polyps, rectal cancer, etc.; vascular lesions such as ischemic enteritis, capillary dilatation, etc., which will lead to a strong positive occult blood in the stool. 2. Middle gastrointestinal diseases: small intestinal diseases such as small intestinal hemangioma, intestinal tuberculosis, intestinal typhoid fever, intussusception; vascular lesions such as ischemic enteritis, etc., all of which will result in strong positive fecal occult blood. 3. Upper gastrointestinal diseases: acute erosive hemorrhagic gastritis, peptic ulcer, gastric cancer, cholangiocarcinoma, rupture and bleeding of esophagogastric fundic varices and esophageal cardia mucous membrane tear syndrome and some other upper gastrointestinal diseases, which can also be manifested as fecal occult blood strong positive. 4. Systemic diseases: leukemia, vitamin C deficiency, hemophilia, etc. can have positive fecal occult blood when manifested as gastrointestinal bleeding. When fecal occult blood is positive, it is recommended to consult a specialist in time, combine with other test results to determine the possible causes of the disease, and follow the doctor’s instructions for further examination and treatment.