Colonoscopy checks for abnormalities in your colon (large intestine) and rectum. Polyps and abnormal tissue are removed during this procedure, making it a cancer prevention tool.

Why it is Done

You might have colonoscopy to:

What to Expect


You must clean out your colon before a colonoscopy.

Usually, this involves:

  • Not eating solid food the day before and drinking only clear liquids
  • Not eating or drinking after midnight the night before
  • Taking a laxative (liquid or pill) the night before and possibly the morning of the exam
  • Giving yourself an enema the night before or possibly the morning of the exam
  • Following your doctor's instructions about which medications you can and cannot take before the exam


The Exam

  • You wear a hospital gown and lie on your side on an exam table.
  • You have sedation medication in pill form or an IV (needle in your arm) to make sure you're comfortable during the procedure.
  • Your doctor inserts a long tube (colonoscope) into your rectum and into your colon. The tube has a light and camera so your doctor can see inside your colon on images transmitted to a monitor.
  • Your doctor can pump air into your colon through the tube to produce better images. You may feel some cramping.
  • Your doctor can insert instruments through the tube to take tissue samples (biopsy) for lab analysis and remove polyps and abnormal tissue.
  • A colonoscopy takes 20 to 60 minutes. Allow another hour or two for recovery from the sedation medication.
  • Someone must accompany you to the exam to drive you home. You can't drive after you've had sedation medication.
  • You may have gas or feel bloated after the exam. Walking can help you feel more comfortable.
  • Your doctor will advise you of any after-care instructions, including dietary modifications.
  • Your first bowel movement after colonoscopy can have a small amount of blood. Contact your doctor if you have blood in your stool after that or have a fever or stomach pain.


  • Negative – No abnormalities are detected. Have another colonoscopy in 10 years unless you have risk factors for colon cancer.
  • Positive – polyps or abnormal tissue is detected.
    • Polyps are analyzed to see if they are cancerous, precancerous or noncancerous (benign).
    • Colon cancer screening may be needed more often based on findings.
    • Surgery may be recommended if abnormal tissue or polyps couldn't be removed during the colonoscopy.

Our gastroenterology specialists are experienced in comprehensive diagnosis and treatment of colorectal problems, including performing colonoscopy.

What the Risks Are

Colonoscopy is generally safe and has few risks. Rare complications include:

  • Bleeding where tissue, tissue sample or polyps were removed
  • Tear in the colon or rectum wall
  • Negative reaction to sedation medication

Find an Aurora Health Care GI Specialist