Hello Katie,

Depending on why you are asking this question there are various reasons. First, colonoscopy is the only way for a doctor to actually see and biopsy (take samples of tissue) the interior of your colon. 

Colonoscopy is most often done when patients are experiencing severe symptoms like chronic diarrhea, blood with bowel movements, severe weight loss, and/or abdominal cramping, among other GI symptoms. The only way for a doctor to know if a patient does or does not have a disease such as Inflammatory Bowel Disease is to do a colonoscopy and take tissue biopsies to check for inflammation in the colon.

Another reason for colonoscopy is to check for colon cancer. From the age of 50 years forward it is recommended that people have routine colonoscopy done with biopsy to check colon health and to make sure there are no colon cancer cells or polyps growing in the GI tract.

Hopefully this answers your question. If not, please be more specific and I'll do my best to help you.

Cheers,

Elizabeth