The following conditions are considered to be the cause of the blood inside the anus: 1. Hemorrhoids, most of which are caused by the patient’s poor diet and lifestyle habits. In severe cases, there is prolapse, enlargement, pain and bleeding of the hemorrhoid nucleus, which is bright red in color and does not blend with the stool. 2. Anal fissure, which is a tear in the skin around the anus caused by the squeezing of dry stool. The amount of bleeding is usually small and the color of the blood is bright red, accompanied by a strong stinging sensation, pain, which lasts until a period of time after the stool. 3, rectal inflammation bleeding. 4, may also be anal polyps and anal fistula and other conditions, caused by bleeding symptoms. It is best to go to the hospital for anoscopy and then take further treatment measures.