The end of the colon is made of the: Sigmoid colon. Rectum. Anus. During sigmoidoscopy the doctor looks at the end of the colon by inserting a tube with a tiny video camera at the tip of the tube. The tube is called a scope. Because the tube does not go as deep into the column as in colonoscopy, sigmoidoscopy has a lower risk of perforating the colon. For this reason, doctors recommend sigmoidoscopy over colonoscopy for some patients.