Anal fissures and internal hemorrhoids are both common in clinical practice. Anal fissures are characterized by periodic pain, which often accompanies painful symptoms during fissures; internal hemorrhoids bleeding is simply painless blood in the stool. The fact that anal fissures are accompanied by painful symptoms, but internal hemorrhoids do not have painful symptoms, is closely related to the anatomical relationship between the two. Internal hemorrhoids, along with external hemorrhoids and anal fissures, are mainly related to the location above and below the distribution of the dentate line. The area above the tooth line is vegetatively innervated and insensitive, which is the main reason why internal hemorrhoids are not painful. Anal fissures are fissures in the skin of the anal canal below the tooth line, and below the tooth line, they are innervated by the spinal nerve, which is particularly sensitive. Therefore, after a patient presents with a complaint of blood in the stool, it is important to start with the complaint and simply distinguish whether it is bleeding from an anal fissure or internal hemorrhoid based on whether there are accompanying painful symptoms, and it will be easier to distinguish after understanding the anatomical relationship clearly.