A colonoscopy is a procedure that uses a colonoscope and a light and camera to look at the bowels. It can help identify colorectal cancer.

Your doctor will check for disease in the colon during a colonoscopy. They will use a colonoscope that has a light and camera attached.

The colon helps form the lowest portion of the gastrointestinal tract. It takes in food, absorbs nutrients, and disposes of waste.

The colon is attached to the anus via the rectum. The anus is the opening in your body where feces are expelled.

During a colonoscopy, your doctor may also take tissue samples for biopsy or remove abnormal tissue such as polyps.

A colonoscopy can be performed as a screening for colorectal cancer and other problems. The screening can help your doctor:

The American College of Surgeons estimates that 90 percent of polyps or tumors can be detected through colonoscopy screenings.

The American College of Physicians recommends a colonoscopy once every 10 years for people who meet all the following criteria:

  • Are 50 to 75 years old.
  • They are at an average risk of colorectal cancer.
  • A life expectancy of at least 10 years is what it should be.

The British Medicine Journal (BMJ) recommends a one-time colonoscopy for people who meet all of these criteria:

  • Are 50 to 79 years old.
  • They are at an average risk of colorectal cancer.
  • There is a chance of colorectal cancer for at least three years.

The American Cancer Society (ACS) and the U.S. Preventive Services Task Force recommend beginning screen at 45 years old, so speak with your doctor to determine when you should start screenings based on your needs.

If you’re at an increased risk for colorectal cancer, you may need more frequent procedures. According to the ACS, people who may need to be screened as often as every 1 to 5 years include:

  • People who have had colon cancer.
  • People with a history of colorectal cancer.
  • People with a family history of cancer.
  • people with inflammatory bowel disease (IBD)

Since a colonoscopy is a routine procedure, there are typically few lasting effects from this test. In the vast majority of cases, the benefits of detecting problems and beginning treatment far outweigh the risks of complications from a colonoscopy.

However, some rare complications include:

  • If a biopsy was done, there would be bleeding from the site.
  • A negative reaction to a drug.
  • A hole in the wall or colon.

A procedure called virtual colonoscopy uses CT scans or MRIs to take pictures of your colon. If it is an option and you opt for it instead, you can avoid some of the complications associated with traditional colonoscopy, although bowel prep is still required.

However, it comes with its own disadvantages. For instance, it has slightly less sensitivity in seeing very small polyps when compared to traditional colonoscopies. As a newer technology, it’s also less likely to be covered by health insurance.

Bowel prep for a colonoscopy

Your doctor will give you instructions for bowel preparation (bowel prep). You must have a clear liquid diet for 24 to 72 hours before your procedure.

The typical diet for the preparation of the colon.

  • broth or bouillon
  • It is a type of gum.
  • Coffee or tea.
  • There is no juice that is made from pulp.
  • Sports drinks, such as Gatorade.

If you drink any liquids with red or purple dye, you can cause colon cancer.


Tell your doctor about all the drugs you are taking. Your doctor may tell you to stop taking them if they affect your colonoscopy. These might include:

Your doctor may give you a laxative to take the night before your appointment. An enema may also be recommended in certain cases, to flush out your colon on the day of the procedure.

You may want to take a ride home after your appointment. The sedative you will be given will make it unsafe for you to drive.

How to prepare for a colonoscopy if you’re pregnant

A colonoscopy during pregnancy is typically recommended only when necessary but is relatively safe for both the pregnant parent and the baby. If it’s only for a regular screening, your doctor may ask you to wait until after you’ve given birth.

Since nutrition is so important during pregnancy, you should speak with your doctor about how to prepare your body for the baby and what types of laxatives are safe to take.

  • Just before your colonoscopy, you’ll change into a hospital gown. Most people have sedation and pain medication. Typically, this is in the form of monitored anesthesia, but lower levels of sedation may also be available upon request and in consultation with your doctor.
  • You will lie on your side on a table during the procedure. If you want a better angle to your colon, your doctor may position you with your knees close to your chest.
  • While you are on your side, your doctor will guide the colonoscope through the rectum and into the colon. A camera on the end of the colonoscope is used to take pictures.
  • Your doctor will inflate your colon using carbon dioxide once the colonoscope is positioned. This gives them a better view.
  • During this procedure, your doctor may remove a sample for a biopsy.
  • The entire procedure takes 15 minutes to an hour.

After the procedure is over, you will wait for about an hour to allow the sedative to wear off. You should not drive for the next 24 hours.

If your doctor removes tissue or a polyp, they will send it to a laboratory for testing. Your doctor will give you the results within a few days.

Colonoscopy results

Some of the results you may receive after a colonoscopy are listed here.

  • Normal findings or negative results: No abnormalities were discovered. If you have average risk of colorectal cancer, your doctor will likely suggest having the next screening in 10 years.
  • Colonic polyps: A growth of tissue in the colon lining. These can either be benign (noncancerous) or neoplastic (cancerous or precancerous). Smaller polyps can often be removed during the procedure, though larger ones may require surgical intervention. A history of polyps may require more frequent screenings.
  • Other potential results: such as diverticular disease (small sacs pushed out against the colon lining), hemorrhoids (swollen veins around the anus or in the rectum), inflammation, or fistulas (abnormal openings in your digestive tract).

You will likely have some gas and a lot of phlegm from the gas your doctor put into your colon. Give yourself time to get out of your system. If it continues for a while, it could mean there is a problem and you should talk to your doctor.

A small amount of blood is normal after the procedure. If you do, call your doctor.

  • continue to pass blood or blood clots
  • It is possible to experience abdominal pain.
  • have a fever over 100°F (37.8°C)

How long does a colonoscopy take?

A typical colonoscopy takes about 15 minutes to an hour, depending on whether the doctor has to remove any polyps or tissue for a biopsy. Plan to spend a few hours at the hospital or endoscopy clinic in total to account for preparation and recovery from the sedative.

Are colonoscopies painful?

Colonoscopies are not typically painful since the sedative will prevent you from remembering the procedure. If you aren’t in the United States, speak with your doctor about what options are available for pain management if a sedative isn’t an option. There could be some mild discomfort in the rectum or stomach after the procedure as well as some bloating from the carbon dioxide.

At what age should I start getting colonoscopies?

If you are at average risk for colorectal cancer, some organizations recommend that you have a colonoscopy every 10 years. Some organizations have recommended starting screenings at 45 years old.

“When to start screenings depends on your doctor’s opinion.”