Frequent waking up in the middle of the night with internal anal distension may be caused by hemorrhoids, infectious diseases, intestinal diseases and other reasons. 1. Hemorrhoids: when hemorrhoids are serious and lead to hemorrhoidal core infection, under the stimulating effect of the source of infection, it may cause anal distension and pain, which may cause frequent waking up in the middle of the night with internal anal distension and pain, and may be accompanied by constipation, blood in the stool and other symptoms. 2. Infectious diseases: common in sinusitis, perianal abscess, such as perianal abscess, especially high perianal abscess, easy to lead to anal distension, may cause frequent waking up in the middle of the night with anal distension and pain, may also be accompanied by perianal itching, pain and other symptoms. 3. Intestinal diseases: commonly seen in proctitis, colitis, intestinal tumors and other diseases, in the inflammation stimulation or tumor pressure stimulation, may lead to frequent waking up in the middle of the night anal distension, may also be accompanied by blood in the stool, abdominal pain and other symptoms. Often wake up in the middle of the night with anal distension and pain, may also be caused by other reasons, if accompanied by other symptoms, should be as soon as possible to consult a doctor, diagnose the cause of the disease, give targeted treatment to avoid delays in the condition.