What are the two lower gastrointestinal system procedures that involve an endoscope and why they are done?

The two lower gastrointestinal procedures that involve an endoscope are colonoscopy and flexible sigmoidoscopy. A colonoscopy examines the entire colon and is typically performed to screen for colorectal cancer, investigate gastrointestinal symptoms, or remove polyps. Flexible sigmoidoscopy focuses on the lower part of the colon (sigmoid colon) and is often used to assess rectal bleeding or other lower GI issues. Both procedures allow for direct visualization and potential biopsy of abnormal tissues.