Colonoscopy is a test that lets your doctor examine the inside of the colon with a camera attached to a small flexible tube. Growths in the intestine (polyps) found during the procedure are removed, possibly preventing cancer from developing. Colonoscopies are recommended beginning at age 50 as a screening for colorectal cancer. A colonoscopy may be recommended for abdominal pain, chronic constipation, chronic diarrhea and rectal bleeding.

what to expect

Before a colonoscopy, you will need to avoid solid food the day before (you can drink only clear liquids) and you will need to fast completely the night before. You’ll also have to take a liquid or pill laxative the night before (and possibly the morning of the exam, too) to clean out your colon. Your doctor might also make adjustments to your usual medications before the procedure.

Here are the instructions for different types of colonoscopy preparations:

During the colonoscopy, you’ll receive medication via a needle in your arm (IV) to sedate you and make you comfortable during the procedure. Then a long tube (colonoscope) is inserted into your rectum and colon. The tube has a light and camera so your doctor can see inside your colon on a monitor. To get clearer images, your doctor can put air into your colon through the tube, which may cause some cramping. Your doctor can insert instruments through the tube to take tissue samples (biopsy) or to remove polyps. 


The colonoscopy takes about 30 minutes, after which you’ll be in a recovery room for about an hour while the sedation wears off. You’ll need someone to drive you home. Afterward, you may pass some air. Your doctor will give you instructions for when you go home. Typically you can resume your usual diet at home that day, but you may not work, drive, or operate machinery.

Results of the test can be:

  • Negative: There were no abnormalities detected, and you don’t need another colonoscopy for 10 years unless you have risk factors for colon cancer.
  • Positive: Polyps or abnormal tissue are detected. In that case, polyps will be checked in the lab to see if they’re noncancerous (benign), precancerous or cancerous (malignant). You might need surgery if abnormal tissue or polyps were found and couldn’t be safely removed during the procedure. Depending on the findings, you might need screenings more often.

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