The rectum is an organ located in the abdominal cavity, connecting the colon and the anus. The rectum is a straight intestine about 11 - 15cm long, the first part of the rectum is shaped like a sigmoid, the last part of the rectum expands to form the rectal ampulla. The main function of the rectum is to store waste. At the same time, it participates in the elimination process. However, this organ often suffers from diseases such as ulcers, polyps, cancer, ...