Hemorrhoid surgery after 1 month is still swelling, in addition to physiological and anatomical reasons, more consideration of inflammatory stimulation, trauma edema and so on. 1. Physiological and anatomical reasons: hemorrhoid surgery surgery area is mainly in the dentate line below the anal canal, the site of the perianal nerve distribution, pain sensitivity, local damage can produce swelling and pain. 2. Inflammation stimulation of perianal skin: due to hemorrhoid surgery for open surgery, so the wound is susceptible to bacterial infection, the formation of inflammation and further stimulation of the perianal skin nerves, resulting in the contraction of the external anal sphincter and the anal muscle, causing swelling and pain. 3. Edema of the trauma: the venous concentration of the anal canal at the dentate line, lymphatic tissue fluid reflux is rich, affected by the surgery, easy to form trauma edema, the patient is conscious of swelling and pain and other discomforts. After hemorrhoid surgery, if you have perianal discomfort symptoms, you should go to the hospital in a timely manner to clarify the cause of the disease, follow the doctor’s instructions to give targeted treatment.