The reasons of anal falling caused by clinical manifestation of rectal cancer may be due to rectal cancer stimulation, rectal tumor at the lower end of rectum and so on. 1. Stimulation of rectal cancer: rectal cancer may be caused by genetic factors, environmental factors, bad dietary habits, etc. Early stage may have no obvious discomfort, with the growth and enlargement of cancerous tissues, the occupation, stimulation, and ulceration of intestines and mucous membranes will cause symptoms such as blood in stools, increase in the frequency of stools, anal dropping and swelling. 2. Intestinal tumor at the lower end of rectum: Intestinal tumor is usually caused by rectal polyps, long-term inflammatory lesions in intestine and stomach. Generally speaking, early rectal cancer with intestinal tumor at the lower end of rectum will lead to swelling in anus and not accompanied by other symptoms. Once rectal cancer is detected, patients are recommended to go to the hospital for further examination in time to make clear the degree of development of the disease, and then go through standardized and reasonable treatment under the evaluation and guidance of professional doctors. In daily life, patients should take appropriate exercise to strengthen their physical condition, quit smoking and drinking, and follow the doctor’s instruction actively to improve the quality of life.