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What Is A Colonoscopy?

A Colonoscopy Is Done For Colon Cancer Screening And Diagnosis Of IBD, IBS


Updated June 02, 2014

What A Colonoscopy Is

A colonoscopy is a test to examine the inside of the colon which can go beyond the areas a sigmoidoscopy can reach. This test uses a colonoscope, which is a flexible tube with lenses, a tiny TV camera and a light at the end. Through fiber-optic technology and a video computer chip, the colonoscope can scan the inside of the colon and transmit images to a video screen.

The colonoscopy procedure can take up to 1 ½ hours and is performed in a hospital as an outpatient procedure. You will be sedated to lessen any discomfort while the doctor checks your colon for:

  • cancer
  • bleeding
  • ulcers
  • abnormal growths (polyps)

What A Colonoscopy Is Used For

A colonoscopy is useful in detecting colon cancer, ulcers, inflammation and other problems in the colon. For colon cancer screening, a sigmoidoscopy is recommended every 3 to 5 years, and a colonoscopy every 10 years after age 50.

Both tests should be performed at a younger age for people with a high risk of colon cancer due to family history, inflammatory bowel disease, a history of cancerous growths or adenomatous polyps, and hereditary syndromes such as familial adenomatous polyposis. Women with a history of ovarian, endometrial or breast cancer may need more frequent colonoscopies.

A colonoscopy can also identify the source of rectal bleeding or identify areas of inflammation in the colon. An attachment at the end of the colonoscope may be used to take a biopsy of the tissue in the colon. If a polyp is found, it may be removed using a wire loop attachment on the colonoscope. Both biopsies and polyps will be sent to a laboratory for further testing.

How To Prepare For A Colonoscopy

In order for the doctor to get a good look at the intestinal wall, the colon must be fairly empty. Your doctor will give you specific instructions on how to use laxatives and enemas before the procedure to cleanse the bowel. It may also be necessary to follow a liquid diet for 1 or 2 days before the procedure, and fast after midnight the night before the test. You will be sedated during the procedure, so you should arrange for someone to take you home and help you to follow instructions.

How A Colonoscopy Is Done

You will be asked to dress in a hospital gown, and an assistant will take your temperature, blood pressure, and respiratory rate (number of breaths per minute). Electrocardiograph (EKG) recording patches may be placed on your chest to monitor your heartbeat, and a pulse oximeter (a device that measures oxygen in your blood) may be placed on your finger.

Next you will be asked to lie on your left side on the exam table. Medication will be given to limit any discomfort experienced during the procedure. Then, the doctor will insert a flexible colonoscope into your rectum. To get a clearer view, some air may also be pumped throught the colonoscope to open up the intestinal passage. Biopsies may be taken from the inside of the colon at this time.

Colonoscopy Risks

There is a risk that the bowel could get punctured during this procedure, but it is uncommon.

Follow Up After A Colonoscopy

You will still feel drowsy after the procedure is over, so someone will need to take you home. This person can also help you remember any instructions given by the doctor after the exam. Your normal diet can be resumed immediately. Call your doctor in a few days for results of any biopsies that may have been taken.

When To Call The Doctor

Call your doctor immediately if you experience:

  • rectal bleeding
  • faintness
  • dizziness
  • shortness of breath
  • heart palpitations

Check with your doctor if you experience:

  • nausea
  • vomiting
  • cramps
  • abdominal pain
  • fever
  • chills
  • severe headache
  • muscle aches


The Cleveland Clinic Information Center. "Colonoscopy Procedure". The Cleveland Clinic. 2013. 30 Sep 2013.

Daus Mahnke, MD. Colonoscopy. NYU Health Center. 2013. 30 Sep 2013.

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