Catherine Spader, RN

What is a colonoscopy?

A colonoscopy is a procedure that examines the lining of your colon and rectum using a thin, flexible instrument called a colonoscope. The colonoscope has a camera that transmits pictures of the inside of your colon to a video screen.

The colon and the rectum make up the large intestine, sometimes called the large bowel. The large intestine is a long, hollow organ in your abdomen that plays an important role in digestion by removing water from digested material and forming feces.  

A colonoscopy is an important test that can detect colorectal cancer in its earliest, most curable stage. It also helps diagnose unexplained intestinal symptoms, such as changes in your bowel movements, abdominal pain, or rectal bleeding. 

Colonoscopy is only one method used to test for colon cancer. Discuss all the screening and testing options with your doctor to understand which options are right for you.

Types of colonoscopy

The types of colonoscopy procedures include:

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  • Colonoscopy is an endoscopy procedure that involves inserting a colonoscope into the large intestine through the anus. The colonoscope contains a camera that transmits pictures of the inside of your colon to a video screen.

  • Virtual colonoscopy is a type of computerized tomography (CT) scan that uses X-rays to produce images of the inside of the large intestine. Despite its name, virtual colonoscopy is not an actual endoscopy procedure because it does not involve inserting a colonoscope into the large intestine.

Other procedures that may be performed

Your doctor may perform other procedures in addition to colonoscopy to diagnose or treat certain conditions. These include:

  • Control of bleeding in the large intestine. This involves injecting medications, applying clips, or sealing bleeding vessels with heat

  • Removal of colon polyps, which are abnormal growths in the large intestine that can become cancerous

  • Tissue biopsy, which involves removing polyps or samples of abnormal looking intestinal tissues. Tissues are examined and tested in a lab for cancer and other diseases.

Why is a colonoscopy performed? 

Your doctor may recommend a colonoscopy to diagnose and treat diseases and conditions of the colon and rectum including:

  • Abdominal pain if the underlying cause has not been found through less invasive testing. Abdominal pain can be caused by many different conditions, such as inflammatory bowel disease, diverticulitis, and intestinal ulcer.

  • Anemia (low red blood cell count) if the underlying cause has not been found through less invasive testing. A colonoscopy can be used to identify potential bleeding sites.

  • Bleeding symptoms, such as rectal bleeding, bloody stool, or black, tarry feces. Potential causes include colon cancer and intestinal inflammation or damage.

  • Bowel movement changes, such as pencil thin stools. Bowel movement changes are caused by various conditions, such as intestinal inflammation and colon cancer.

  • Colon polyps, abnormal growths in the large intestine that can become cancerous. In some cases, polyps are first identified during another procedure called a barium enema and removed during colonoscopy.

  • Colorectal cancer screening. A colonoscopy can identify and remove abnormal tissue and colon polyps before they develop into cancer.

  • Diarrhea. A colonoscopy can identify inflammation and infections.

  • Diverticulosis and diverticulitis, intestinal pockets that can develop over time and can become infected or cause bleeding

  • Inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease

  • Unexplained weight loss if the underlying cause has not been found through other, less invasive tests

Who performs a colonoscopy?

The following doctors commonly perform colonoscopies:

  • Gastroenterologists are internists who specialize in diseases of the intestines. Gastroenterologists perform most colonoscopies.

Other doctors who perform colonoscopies: 

  • Colon and rectal surgeons are general surgeons with extra training in the surgical treatment of intestinal and rectal conditions.

  • General surgeons specialize in the surgical treatment of a variety of diseases, disorders and conditions. Some general surgeons focus their practice on the intestinal tract.

How is a colonoscopy performed?

Your colonoscopy will be performed in a hospital or outpatient setting. The procedure takes about 30 minutes and generally includes these steps:

  1. You will dress in a patient gown.

  2. You will lie on your left side on a procedure table and pull your knees up to your chest.

  3. You will have a light sedative to make you drowsy and relaxed and a pain medication. Deeper sedation or anesthesia is sometimes used, which makes you more relaxed and unaware of the procedure.

  4. Your doctor will gently insert the colonoscope through the anus and into the rectum and colon. The image is transmitted onto a video screen.

  5. Your doctor will insert air into the colon. Stool and fluids are removed through the colonoscope as needed. This improves the view of the intestinal lining.

  6. Your doctor will slowly and gently pull the colonoscope out of the colon and rectum, examining it for any abnormalities. This is when the most careful examination is carried out and images are taken. Other procedures may be performed during this time, such as a tissue biopsy.

Will I feel pain?

Your comfort and relaxation are important to you and your care team. You may feel pressure and brief cramping during the procedure. Your doctor will give you enough pain and sedative medications so you stay comfortable. Tell your doctor if you are uncomfortable in any way.

What are the risks and potential complications of a colonoscopy?  

Complications of a colonoscopy are uncommon, but any procedure involves risks and the possibility of complications that may become serious in some cases. Complications can develop during the procedure or recovery. Risks and potential complications of a colonoscopy include: 

  • Adverse reaction or problems related to sedation or medications, such as an allergic reaction and problems with breathing

  • Bleeding

  • Dehydration due to taking enemas and laxatives before the procedure

  • Gastrointestinal disturbances, such as nausea, vomiting, and rectal discomfort

  • Infection

  • Puncture of the large intestine

Reducing your risk of complications

You can reduce the risk of certain complications by: 

  • Following activity, dietary and lifestyle restrictions and recommendations before your procedure and during recovery

  • Notifying your doctor immediately of any concerns, such as bleeding, fever, or increase in pain

  • Taking your medications exactly as directed

  • Telling all members of your care team if you have any allergies

How do I prepare for my colonoscopy?

You are an important member of your own healthcare team. The steps you take before your colonoscopy can improve your comfort and help get the most accurate test results. 

You can prepare for a colonoscopy by:

  • Answering all questions about your medical history and medications. This includes prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times.

  • Completely cleansing your intestines as directed by your doctor