They say anal fissures hurt, but how much do you really know about them? Anal fissures are fissures that occur in the whole layer of the skin of the anal canal. The cause is mostly due to dry stools. It occurs mostly in the posterior or anterior position of the anus. Both men and women, young and old, can suffer from this disease. Anal fissures are prismatic fissures or ulcers formed by rupture of the skin of the anal canal below the dentate line. It is a common anal canal disease that occurs in young adults, but also in children and less frequently in the elderly. According to statistics in Europe and the United States, women get this disease more often than men, and according to clinical observation in China, men are more common than women. Anal fissures often occur in the back and front of the anus, mostly in the back of the anus, and less often in both sides. At first, there is only a small fissure on the skin of the anal canal, sometimes it can be cracked to the subcutaneous tissue or to the superficial layer of the sphincter, and the fissure is linear or prismatic, if the anus is opened, the fissured wound becomes round or oval. Pain is the main symptom of anal fissure. Most patients feel pain when defecating, and there is a short interval of pain relief after defecation, followed by continuous and increasing pain. The duration of pain varies depending on the extent of the fissure and can last from a few hours to a full day. The main cause of the severe pain is the stimulation of the nerve endings in the fissure during defecation, which immediately causes burning and cutting pain in the anus, resulting in spasmodic contraction of the internal anal sphincter, leading to persistent pain. Then, as time passes, the sphincter gradually becomes fatigued and relaxes, and the pain then decreases and gradually disappears. This is called “a cycle of pain” in anal fissure pain symptoms. In addition, not only can feces cause severe pain in anal fissures, but coughing, sneezing, and urination can also cause this pain cycle. If the early stage of anal fissure is not treated in time, three conditions may appear, such as anal canal ulcer (fissure fibrosis, also known as old fissure), anal papilloma (polypoid tumor), and sentinel hemorrhoid (dermal hyperplasia), which may also develop into anal sinusitis (chronic inflammation of the anus) and anal fistula (purulent inflammation of the anus). The first three are called the “five features of anal fissure”. There is also the possibility of becoming anal canal cancer due to long-term chronic inflammatory stimulation.