What is the purpose of getting a colonoscopy?

Multiple purposes: The primary purpose is to screen for colon and rectal cancer. The physician is looking for polyps or other growths and will either completely remove them or get adequate biopsies so the pathologist can determine if they are benign or not. Other things that can be seen include diverticula, abnormalities of blood vessels in the colon wall, and signs of inflammation indicative of colitis.