There are several common causes of blood in the stool but not painful: 1. It is more common to see bleeding caused by hemorrhoids, especially internal hemorrhoids. If the amount of blood in the stool is bright red, in the form of drops or jets, especially when the amount of blood in the stool increases, it is possible that the bleeding is caused by internal hemorrhoids, and anoscopy can clearly see that the hemorrhoid nucleus is bruised, swollen and hemispherical. 2. If the blood in the stool is dark red, consider that the bleeding site is far from the anus, it may be bleeding from the upper gastrointestinal tract, or it may be bleeding caused by gastroduodenal ulcers or small intestinal lesions. If the patient has a malignant tumor of the colon or rectum, it can also lead to the erosion of the blood vessels under the rectal mucosa and cause blood in the stool, without painful symptoms.