The etiology of intra-anal swelling is relatively varied and may be caused by anal inflammation, anal prolapse, chronic inflammation of the rectum and other diseases. 1. Anal inflammation: when the mucous membrane and perianal skin in the anal area are infected, especially when there is abscess in the area above the anal raphe muscle, the local swelling and stimulation of the local nerves can lead to a feeling of falling in the anus. 2. Morphological changes of the anus: when the morphology of the anus changes, resulting in the mucous membrane layer of the rectal wall or the whole layer of the intestinal wall pushes downward, making the patient in defecation or abdominal pressure increases when anal prolapse occurs, the patient can feel the anal drop. 3. Chronic inflammation of the rectum: chronic inflammation of the rectum, such as chronic colitis and other inflammatory diseases involving the rectum, can also stimulate the nerves leading to increased defecation and the emergence of the anus falling sensation. When the anal swelling, such as can not be relieved, it is recommended that patients go to the hospital in a timely manner for examination, to clarify the specific causes and give targeted treatment to avoid aggravation of the condition.