Version July 2025
During a colonoscopy or a sigmoidoscopy, you lie on your side. The doctor puts a thin tube with a camera into your anus (from behind). The tube is called a "scope." The doctor then moves the scope up into the rectum and colon. The camera sends pictures from inside your colon to a screen for the doctor to see.
A colonoscopy allows the doctor to see the whole colon (shown in pink and green). A sigmoidoscopy allows the doctor to see only part of the colon (shown in only green, up to the arrow).