The lower and middle rectum and the anus are completely different from the concept of the digestive tract in the general sense; they are a unique organ of stool control with biological and sociological significance. This organ is anatomically and physiologically composed of the lower and middle rectum, the anal canal, and the neuromuscular structures that control defecation and the corresponding sensations. Effective preservation of this organ not only has a great impact on the patient’s quality of life, but also on the patient’s social activities, family life, and personal self-esteem. Due to the common nature of rectal diseases, preservation of the anus has always been a common choice problem for both patients and doctors.