Blood at the anal opening during defecation is still relatively common in daily life. The common diseases are: the first one, consider internal hemorrhoids, is the most common in clinical practice. There is blood at the anal opening before or after defecation, and the bleeding is fresh and can be dripping or squirting. There are usually no painful symptoms and the bleeding can be more or less. The second, anal fissure, usually occurs after a bowel movement with blood at the anal opening, the amount of bleeding is relatively small, but there is a moderate amount of pain at the anal opening, usually occurs after constipation. The third one is trauma to the rectal mucosa, which is caused by the tearing of the rectal mucosa by hard stool after constipation. Neither internal hemorrhoids nor anal fissures, or simple trauma to the rectal mucosa, can also occur after a bowel movement with blood at the anal opening. The fourth one, rectal cancer. Difficult stool, bleeding from the anal opening, blood is dark red, not the same as internal hemorrhoids. The fifth, proctitis, especially ulcerative proctitis, bleeding from the anal opening after stool, is dark red pus and blood stool, mucus and blood stool.