The colon is the lowest portion of the gastrointestinal tract that takes in food, absorbs nutrients and disposes of waste. A thin, flexible camera on the end of a tube, called a colonoscope, is used to check for abnormalities or disease in your lower intestine or colon. Colonoscopy can be done as a screening for colon cancer, to explore the cause of unexplained changes in bowel habits, evaluate symptoms of pain or bleeding located in the abdominal area, and find a reason for weight loss, chronic constipation or diarrhea