Rectum is the last section of the human digestive system, horizontal position in the human body from the third sacral position, on the sigmoid colon, connected to the anus, the normal rectum length of about 12-15cm, to the pelvic septum as the boundary, the rectum can be roughly divided into upper and lower parts, the upper part clinically known as the pelvic part, the lower part is called the anal canal and the anus part. The lower part of the pelvic region is characterized by a pike-shaped bulge, which is mainly used for storing feces and is clinically known as the recto-pelvic abdomen. The rectum, despite the word straight in its name, is not completely straight; there are two curves and three transverse folds in the anterior-posterior direction, the upper curve being the rectosacral curve, which protrudes posteriorly, and the lower curve being the perineal curve, which protrudes anterolaterally and is mainly used to support feces. Particular care needs to be taken to avoid damage to the inner wall of the curvature when performing examinations such as proctoscopy.