What is a colonoscopy?

It's a procedure that allows your doctor to examine the inside of the colon to check for abnormalities, such as polyps. During a colonoscopy, a thin, flexible tube (colonoscope) is passed through the rectum into the colon (large intestine). The tube has a tiny camera that allows the doctor to view this area and identify, test or remove any polyps or other abnormalities. Removing polyps helps to prevent colon cancer.

What are polyps in the colon?

A polyp is a small clump of cells that forms on the lining of the colon. Most colon polyps are noncancerous, but over time some types can become cancerous. Removing polyps is the best way to prevent cancer from developing. Polyps typically don’t cause symptoms, which is why it’s so important to have regular colonoscopy screenings.

How a colonoscopy is performed

You will be asked to lie on your left side with your knees drawn up toward the abdomen. After administration of an intravenous sedative and analgesic, the colonoscopy instrument is inserted through the anus and gently advanced under direct vision to the terminal small bowel.

During the colonoscopy, air will be inserted through the scope to provide a better view. Suction may be used to remove secretions.

Since better views are obtained during withdrawal than during insertion in a colonoscopy procedure, a more careful examination is done during withdrawal of the scope. Tissue samples may be taken with tiny biopsy forceps inserted through the scope. Polyps can be removed with electrocautery snares, and photographs can be taken.

How to prepare for a colonoscopy

Your bowel needs to be completely empty and clean for the exam. A problem in your large intestine that needs to be treated may be missed if your intestines are not cleaned out.

Your health care provider will give you the steps for cleansing your bowel. This is called bowel preparation. Steps may include:

  • Using enemas
  • Not eating solid foods for 1 to 3 days before the test
  • Taking laxatives

You need to drink plenty of clear liquids for 1 to 3 days before the test. Examples of clear liquids are:

  • Clear coffee or tea
  • Fat-free bouillon or broth
  • Gelatin
  • Sports drinks without added color
  • Strained fruit juices
  • Water

You will likely be told to stop taking aspirin, ibuprofen, naproxen, or other blood-thinning medicines for several days before the test. Keep taking your other medicines unless your doctor tells you otherwise.

You will need to stop taking iron pills or liquids a few days before the test, unless your provider tells you it is OK to continue. Iron can make your stool dark black. This makes it harder for the doctor to view inside your bowel.

How a colonoscopy will feel

The medicines will make you sleepy so that you may not feel any discomfort or have any memory of the test.

You may feel pressure as the scope moves inside. You may feel brief cramping and gas pains as air is inserted or the scope advances. Passing gas is necessary and should be expected.

After the exam, you may have mild abdominal cramping and pass a lot of gas. You may also feel bloated and sick to your stomach. These soon go away.

You should be able to go home 1 hour after the test. You must plan to have someone take you home after the test, because you will be woozy and unable to drive. The providers will not let you leave until someone arrives to help you.

When you are home, follow instructions on recovering from the procedure. These may include:

  • Drink plenty of liquids. Eat a healthy meal to restore your energy.
  • You should be able to return to your regular activities the next day.
  • Avoid driving, operating machinery, drinking alcohol, and making important decisions for at least 24 hours after the test.

Is a colonoscopy painful?

Most people choose to be under sedation during the procedure and don’t remember any of it when they wake up. Sometimes people experience a bit of gas pain afterwards from having air inserted into the colon during the procedure, but that’s usually it.

Why is a colonoscopy performed?

Colonoscopy may be done for the following reasons:

  • Abdominal pain, changes in bowel movements, or weight loss
  • Abnormal changes (polyps) found on sigmoidoscopy or x-ray tests (CT scan or barium enema)
  • Anemia due to low iron (usually when no other cause has been found)
  • Blood in the stool, or black, tarry stools
  • Follow-up of a past finding, such as polyps or colon cancer
  • Inflammatory bowel disease (ulcerative colitis and Crohn disease)
  • Screening for colorectal cancer

Virtual colonoscopy

A virtual colonoscopy uses CT scan technology to visualize the colon. The major benefit of the virtual colonoscopy is that it’s a non-invasive procedure.

An alternative to traditional colonoscopy,  virtual colonoscopy (VC) is the newest screening test for colorectal cancer. VC was developed at Wake Forest Baptist Medical Center. Virtual colonoscopy uses a helical CT scanner to take images of the colon. Special computer software converts this information into a three-dimensional image of the colon that a radiologist can scan for abnormal growths.

Currently, virtual colonoscopy is most accurate at ruling out cancer and abnormal growths. This is most important because 80 percent of adult patients do not have significant polyps. If an abnormality is found, the patient also undergoes a traditional colonoscopy, in which a flexible fiber-optic tube is inserted into the colon.Virtual colonoscopy is still in its early development so long-term data for accuracy is not available. Studies do show, however, that it is important to have a virtual colonoscopy procedure done at a center that has physicians experienced in performing the procedure and evaluating the results. 

What do abnormal colonoscopy results mean?

Abnormal test results may mean any of the following:

  • Abnormal pouches on the lining of the intestines, called diverticulosis
  • Areas of bleeding
  • Cancer in the colon or rectum
  • Colitis (a swollen and inflamed intestine) due to Crohn disease, ulcerative colitis, infection, or lack of blood flow
  • Small growths called polyps on the lining of your colon (which can be removed through the colonoscope during the exam)

When do I need to see a colorectal surgeon? 

If cancerous polyps are suspected and your gastroenterologist determines that colorectal surgery is needed for further diagnosis or to remove cancerous tissue, they’ll refer you to a colorectal surgeon.

Am I at risk for colon cancer?

Everyone is at risk. Colon cancer is the third most common type of cancer in both men and women and is the second-leading cause of cancer deaths in the United States. You're at higher risk if you:

  • Have Crohn's disease or ulcerative colitis
  • Are between the ages of 45 to 75
  • Have a family history of colon cancer or precancerous polyps

I don’t have symptoms, so I don’t need a colonoscopy, right?

False. Symptoms usually don’t appear until the later stages of colon cancer. But when it’s detected early, colon cancer is one of the easiest cancers to treat. That’s why regular colonoscopy screenings are so important.