A colonoscopy is a medical procedure that allows imaging of the lower bowels so a doctor can make a diagnosis by actually looking for physical problems or defects. The procedure involves inserting a flexible camera into the lower bowel via the anus. Usually the doctor will also take biopsy samples while inspecting the bowel. Colonoscopies are usually done either under sedation or anesthesia.
Disclaimer: I am not a medical professional. Using this information is at your own risk.