Anal distension is considered to be thrombosed external hemorrhoids and the presence of abscesses around the anus. Anal swelling and pain is more common in daily life, and most patients with anal swelling and pain should consider it caused by two conditions: one, when there is an anal abscess that can easily lead to local swelling and pain. Perianal abscess is an acute infectious disease, secondary to inflammation of the anal glands, prone to recurrent episodes of abscess formation, the patient will experience chills, fever, significant swelling and edema around the anus, and sometimes significant tenderness, the acute phase should be treated by surgical incision and drainage. Second, in addition to perianal abscess, patients with thrombosed external hemorrhoids have dark purple abscess formation around the anus after constipation, which leads to obvious swelling and pain around the anus due to swelling or inflammation stimulation, and also have blood in the bowel movement or local swelling and pain symptoms.