unexplained anemia, unexplained blood in the stool, abdominal pain
, persistent diarrhea, or abnormalities (such as polyps
) found on contrast x-rays or inflammatory bowel disease. This procedure is also used in obtaining tissue specimen for biopsy.
And most importantly, colonoscopy is advised to everyone, age 50 years old and above, to screen for colorectal cancer.
You can learn more about this through this link: http://www.nlm.nih.gov/medlineplus/ency/article/003886.