Rectal potbelly is located in the middle and lower part of the rectum, from the anal verge of 3~10cm, is the anatomical concept, but also the incidence of rectal lesions. Rectum is located in the pelvic cavity, divided into upper middle and lower three sections, the upper rectum and sigmoid colon connected to the lower rectum and the continuation of the anal canal, and the sigmoid colon at the junction of the upper rectum diameter is thin, the middle of the rectum down the intestinal lumen is significantly enlarged, the lower rectum to the anal canal and significantly narrowed, the middle enlarged part of the rectum known as the jugular abdominal area of the rectum. Rectal jugular abdominal area is the internal hemorrhoids, anal fistula and rectal cancer of the good parts, because the rectal jugular abdominal area from the anal verge of the proximity of the rectal fingerprinting, proctoscopy or sigmoidoscopy can be understood by its lesions.