Sudden cramp-like pain in the anus can be seen in the following diseases: 1. inflammatory perianal diseases, such as anal sinusitis, anal papillitis, external hemorrhoid inflammation, anal fistula infection and other inflammatory diseases. Individual cases of pain will be accompanied by systemic symptoms, such as fever, chills, etc.; 2. cramping pain, edema of anal fissure and hemorrhoids; 3. painful anorectal injury, foreign body damage to the anus, anal lacerations. If over-eating spicy and strong alcohol, the stimulating ingredients in the stool will also cause anal pain and discomfort; 4, anal and surrounding tissue pressure pain, such as low rectal cancer; 5, mental factors, if the patient has long-term mental tension, and the formation of anal neurosis; 6, rectal pressure increase pain, such as bacterial dysentery, stimulating the end rectal pressure receptors, and its cause anal cramp-like pain.