Blood in the stool is often seen in the following anorectal diseases: 1, hemorrhoids: mainly caused by internal bleeding hemorrhoids. Mostly seen in adults, less common in children and adolescents under the age of 18. It is mainly intermittent bleeding, bright red, not mixed with the stool, attached to the surface of the stool, or when the stool drops down, or a line like an arrow, or only hand paper stained blood, no pain, or accompanied by anal prolapse, mucus flow, itching, etc. 2.Anal fissure: Anal fissure bleeding is more common in women, especially in middle-aged women. Blood in the stool is bright red, but the amount of bleeding is very small, accompanied by severe pain in the anus during defecation, the pain is slightly relieved after the stool and again severe pain, often lasting several hours. 3, intestinal polyps: intestinal polyps are mostly seen in young people, followed by children, the amount of bleeding can vary. When the polyp is larger, lower or more bleeding, the blood in the stool is not mixed with the stool, attached to the surface of the stool, or even simple blood in the stool. If the polyps are higher and more numerous, the blood often mixes with the stool. Bleeding from intestinal polyps can also be occult, with only red blood cells or positive occult blood test on stool microscopy, mostly seen when the polyps are high or small and few in number. The polyps are usually painless, but low rectal polyps can be seen as flesh-like masses coming out of the anus during defecation. Some can see abdominal discomfort, abdominal pain, shortness of breath and other intestinal irritation, mainly due to intestinal peristalsis pulling polyps. 4, colon cancer, rectal cancer: mostly occurs above 40 years old, but can also occur at any other age, slightly higher in men than in women. Early lesions are limited to the mucosa, no obvious symptoms, cancer development, intermediate ulcers, secondary infections, symptoms begin to appear. The amount of bleeding is usually small, and the stool is either bright red or slightly dark with pus blood and mucus. If there is a change in the nature of the stool, frequent bowel movements or a feeling of impurity after defecation, anemia and weight loss, you should be alert to colon cancer and rectal cancer. 5, ulcerative colitis, Crohn’s disease: ulcerative colitis, Crohn’s disease are unexplained intestinal non-specific inflammatory disease, mostly seen in young people. Mucus blood stool as the main symptom, stool containing blood, pus and mucus, generally not much bleeding, and abdominal pain, diarrhea or diarrhea and constipation alternately, or accompanied by wasting, fatigue, low fever, anemia and other systemic symptoms. 6, other: black stool is mainly seen in the upper gastrointestinal tract diseases, such as inflammation of the esophagus, stomach and duodenum, ulcers, injuries, vascular lesions, tumors, etc., but do not swallow the oral and respiratory bleeding, or a lot of ingestion of animal blood, animal liver and phenolphthalein laxatives caused by black stool mistaken for blood in the stool. Blood in stool accompanied by fever and abdominal pain, and the onset of more rapid, mostly seen in bacterial dysentery, epidemic hemorrhagic fever, hemorrhagic necrotizing enterocolitis, amebic enteropathy, etc.; bleeding volume, rapid onset, accompanied by severe abdominal pain, mostly seen in intussusception, mesenteric artery embolism; accompanied by systemic bleeding tendency, should be considered thrombocytopenic purpura, aplastic anemia, leukemia, hemophilia and other hematologic diseases.