Colonoscopy
A colonoscopy is an exam that looks at the inside lining of the large bowel (colon) and rectum using a colonoscope, a thin flexible tube with a small camera. Tissue samples and polyps can be taken during the same procedure.
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A colonoscopy is an exam that lets a doctor look at the inside lining of the large bowel (colon) and rectum. It uses a colonoscope, a thin flexible tube with a small camera at the tip that can reach along the whole length of the colon (MedlinePlus).
One thing that surprises many people: a colonoscopy is not only a way of looking. Tissue samples (a biopsy) and polyps can be taken or removed during the same procedure, using tiny tools passed through the scope (MedlinePlus).
Why it is done
A colonoscopy is used to screen for colorectal cancer, to find the cause of symptoms like blood in the stool or black, tarry stools, to look for abnormal growths, and to check on inflammatory bowel disease, both ulcerative colitis and Crohn's disease (MedlinePlus). It is one of the most sensitive tests available for colon cancer screening, and because polyps (precancerous growths) can be removed as they are found, the exam can stop a cancer before it starts (Mayo Clinic).
The bowel prep
For the doctor to see clearly, the bowel needs to be completely empty and clean. This is what the preparation is for, and it usually means sticking to clear liquids the day before and taking laxatives to clear the bowel (MedlinePlus). The prep is the part most people find hardest, but it is what makes the exam accurate. Your endoscopy team will give you instructions tailored to your appointment.