Colonoscopy Overview

A colonoscopy is a test that is used to examine the inside of the colon (large intestine). The tool used for this is called 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 of the intestinal wall to a video screen. A gastroenterologist (a specialist in digestive disease) or a colorectal surgeon usually performs the test.

A colonoscopy can be used to diagnose digestive diseases (or rule them out!), and it is also the gold standard for colon cancer screening and prevention. Growths on the inside of the colon, called polyps, are the precursor to cancer, but they can be removed during a colonoscopy. After it's over, most people are surprised at how easy it is to have a colonoscopy and that going back to work or school the next day is not an issue.

Why Have A Colonoscopy?

A colonoscopy is useful in finding colon cancer, ulcers, inflammation, and other problems in the colon. For colon cancer screening, a colonoscopy is recommended every 10 years after age 50 for those at normal risk.

Screening  should be performed at a younger age for people with a high risk of colon cancer due to a family history of colon cancer, inflammatory bowel disease (IBD), a history of cancerous growths or adenomatous polyps, and hereditary syndromes such as familial adenomatous polyposis (FAP).

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.

People with IBD (Crohn's disease and ulcerative colitis) may need a colonoscopy on a regular basis, even as frequently as every year. This is to keep an eye on any inflammation and understand what effect the disease is having on the colon.

The colonoscopy procedure can take up to one and a half hours and is often performed in an endoscopy center or in a hospital as an outpatient procedure. Patients are typically sedated with medication that is given through an IV, which reduces discomfort. Most people don't remember the test because of the "twilight sleep" medication that is used. The physician performing the colonoscopy will check the colon for:

  • colon or rectal cancer
  • bleeding
  • ulcers
  • abnormal growths (polyps)

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 of stool.

Your doctor will give you specific instructions on how to use laxatives and enemas before the procedure to cleanse the bowel. Doctors may prescribe different techniques for certain patients. For example, a patient with severe diarrhea may not need as much prep as a person with a healthier bowel. 

It may also be necessary to follow a liquid diet for one or two days before the procedure, and fast after midnight the night before the test. By following the doctors' instructions correctly, the large intestine will be clean and free of waste, so any ​pathology can be more easily seen and diagnosed.

Some patients may also have to stop taking certain medications for a day or two prior to the test. The physician doing the colonoscopy will provide instructions, but it is also important to ask questions about taking any pills before the test. Instructions should be followed carefully because if a prep isn't done correctly the colonoscopy might not be completed and then it will need to be rescheduled. Patients are sedated during the procedure, so someone else has to get discharge instructions and drive home.

What Happens During a Colonoscopy?

Patients are asked to remove all clothing (socks or a bra may be allowed in certain circumstances) and dress in a hospital gown. A healthcare provider will take body temperature, blood pressure, and respiratory rate (number of breaths per minute) readings. Electrocardiograph (EKG) recording patches may be placed on the chest to monitor heartbeat, and a pulse oximeter (a device that measures oxygen in blood) may be placed on the finger.

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

After the test, the IV sedation is reversed and patients spend time in a recovery room. Because the colonoscope introduces air into the colon, there will be some bloating that will be relieved by passing gas out of the bottom. In many cases, some food (such as crackers) and juice is offered to patients while they wake up and get ready to go home. 

Colonoscopy Risks

The risks during a colonoscopy are extremely low. There is a risk that the bowel could get punctured during this procedure, but it is uncommon. While many people cite risks as a reason for forgoing a colonoscopy, in truth the risks are so low that they are not a valid excuse for skipping a colon cancer screening or a regular IBD-related colonoscopy.

Follow-Up After a Colonoscopy

Patients typically feel drowsy after the procedure is over, so a friend or family member will need to drive home. This person can also help remember any instructions given by the doctor after the exam. A normal diet can be resumed immediately after the test. A follow-up with the doctor should be scheduled a few days after the colonoscopy so that any results or biopsy findings can be discussed.

When to Call The Doctor After a Colonoscopy

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

A Word From Verywell

It's true that having a colonoscopy is not what anyone would consider "fun." It is, however, an incredibly useful diagnostic test. Without this test that can screen for cancer as well as remove polyps, more people would develop colon cancer. In addition, people with other digestive diseases might never get an accurate diagnosis or effective treatment. A colonoscopy is definitely a test worth doing when recommended. Most people are surprised at how easy it is, and when used for colon cancer screening, it may not need to be repeated for five or 10 years.

Sources:

AGA Patient Care. Colorectal Cancer Screening and Surveillance for Early Detection. American Gastroenterological Association. 13 Feb 2008.

Centers For Disease Control And Prevention. Colorectal Cancer Tests Save Lives. Vital Signs. 2013.

Mahnke D. Colonoscopy. NYU Health Center. 2013.

National Institute of Diabetes and Digestive and Kidney Diseases. Colonoscopy. National Digestive Diseases Information Clearinghouse. Nov 2014.

The Cleveland Clinic Information Center. Colonoscopy Procedure. The Cleveland Clinic. 2013.

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