What’s the difference between a flexible sigmoidoscopy and a colonoscopy?

A flexible sigmoidoscopy and a colonoscopy are both tests that allow examination of the colon, but they differ in how much of it they examine. A flexible sigmoidoscopy only looks at the lower part of the colon, called the rectum and sigmoid colon, while a colonoscopy examines the entire colon.

Because a colonoscopy inspects the whole colon, it's more comprehensive and can detect abnormalities that a sigmoidoscopy might miss. Both procedures use a thin, flexible tube with a camera, but colonoscopy usually requires more extensive bowel preparation and sometimes sedation.