During a colonoscopy, the patient is given medicine and the doctor inserts a colonoscope, or a thin tube, into the colon, according to the American Cancer Society. The colonoscope has a small video camera at the end that transmits images of the colon to a screen.
The doctor uses the colonoscope to add air to the colon to keep it open so that the images are clear, relates WebMD. At this time, the patient may feel a slight discomfort. When the procedure is completed, the doctor removes the colonoscope, and a sample of tissue from the colon may be sent to a laboratory to make a positive diagnosis. A virtual colonoscopy, which involves the use of a probe and a CT scan, can be done in place of a regular colonoscopy, although both procedures offer similar results.
The procedure takes approximately 30 minutes and is performed every 10 years to check for polyps in the colon and to screen for colon cancer, states the American Cancer Society. Although serious risks are uncommon, they include tearing of the colon and bleeding. Before the procedure, the patient is given instructions to prepare for the colonoscopy, including taking laxatives to make sure the colon is empty. A colonoscopy can be used to form a diagnosis when a patient experiences gastrointestinal problems such as bloody stools or diarrhea, notes MedicineNet.