Anal fissure is a deep and full skin ulcer in the anal canal, mostly in the posterior median area, but a few in the anterior median area. In patients with long-term constipation, the skin of the anal canal is fractured during discharge due to dry and hard feces and excessive force of manganese, and the repeated injury makes the fracture deep to the whole skin. The skin of the posterior middle of the anal canal is more fixed, and the position of the end of the rectum is bent forward from the rear, so the pressure on the rear of the anus is greater, which is a common site for anal fissure. Rough examination can also cause anal fissures. The skin at the lower end of the fissure is edematous due to inflammation, superficial venous and lymphatic reflux obstruction, forming a connective tissue external hemorrhoid, called “anterior sentinel hemorrhoid”. The upper end of the anal fissure becomes a hypertrophic papilla due to inflammation and fibrosis. The typical symptoms are pain, constipation, and bleeding. The pain is relieved for a short time after the feces is expelled, but after a few minutes, the sphincter muscle spasms reflexively, causing intense pain for a longer period of time, and some need to use painkillers to relieve the pain. Therefore, patients with anal fissures are afraid of defecation, making constipation even worse and forming a vicious circle. A small amount of bleeding may occur on the surface of the feces or drip blood after the fissure. The newly occurred anal fissure has neat, soft edges, shallow ulcer base, no scar tissue, red color and easy bleeding. Chronic anal fissures are deep and hard, grayish-white, and do not bleed easily. Below the fissure is the “anterior hemorrhoid”. Anal finger and anoscopy can cause severe pain to the patient and should not be performed. Treatment Fresh anal fissure can be healed by non-surgical treatment, such as local hot water bath or 1:5000 potassium permanganate bath after stool, which can promote the relaxation of anal sphincter. The sphincter can be relaxed with procaine or enema. For old anal fissures, if the above treatment is not effective, surgical excision can be used, including excision of the ulcer together with the skin flap (anterior sentinel hemorrhoid), and part of the external sphincter fibers can be cut, which can reduce postoperative sphincter spasm and facilitate healing. In recent years, liquid nitrogen cryoanal fissure resection has been used to obtain satisfactory results, with the advantages of less postoperative pain, no bleeding of the trauma and no anal incontinence.