Colonoscopy

What It Is

During a colonoscopy, a doctor guides a colonoscope (a thin, flexible tube with a light and camera) through the rectum and into the colon. Images appear on a screen so the doctor can look for inflammation, bleeding, polyps, or cancer.

Because some polyps can turn into cancer over time, finding and removing them is one way colonoscopy can help prevent colorectal cancer. Tissue samples (biopsies) can also be taken during the procedure.

Colonoscopy is usually done by a gastroenterologist or surgeon in a hospital or outpatient endoscopy center, and the exam often takes about 30 to 60 minutes.

Common Terminology

Colonoscope

A long, flexible tube with a light and camera used to see inside the colon.

Bowel prep

The process of cleaning out the colon before the exam, usually with a special liquid laxative and a clear-liquid diet.

Polyp

A growth on the inner lining of the colon. Most are not cancer, but some types can become cancer over time.

Polypectomy

Removal of a polyp during a colonoscopy.

Biopsy

A small sample of tissue taken to be examined under a microscope.

Adenoma

A type of polyp that has the potential to become cancer.

Sedation

Medicine that helps a person relax or sleep lightly during a procedure.

Why It Is Done

A colonoscopy may be done for several general reasons:

• Screening for colorectal cancer in people who have reached the age at which screening is generally recommended.
• Follow-up after a positive result on another screening test, such as a stool test.
• Looking for causes of symptoms such as rectal bleeding, ongoing changes in bowel habits, or unexplained anemia.
• Monitoring conditions such as inflammatory bowel disease.
• Surveillance after polyps or colorectal cancer have been found in the past.

How It Is Performed

This is a general description of a typical exam:

• The person usually lies on their side, and sedation or anesthesia is given through a vein.
• The doctor gently inserts the colonoscope into the rectum and advances it through the colon.
• Air or carbon dioxide is used to open up the colon so the lining can be seen clearly.
• Polyps can be removed and biopsies taken using small tools passed through the scope.
• The exam itself often takes about 30 to 60 minutes.

Before the Procedure

Preparation is an important part of a colonoscopy. In general:

• People receive written bowel prep instructions from their care team, and following them closely helps the exam be accurate.
• A clear-liquid diet is commonly used the day before, and some foods may be limited for a few days earlier.
• The prep drink causes frequent, watery bowel movements, so people often plan to stay near a bathroom.
• The care team typically reviews current medicines, especially blood thinners and diabetes medicines, and gives specific guidance.
• Because of sedation, people are usually asked to arrange for someone to drive them home.

Recovery Overview

After the exam, in general:

• People rest in a recovery area until the sedation wears off, which usually takes an hour or so.
• Bloating, gas, or mild cramping are common for a short time afterward.
• Driving, operating machinery, and making important decisions are generally avoided for the rest of the day.
• Many people return to their usual diet soon after the procedure unless told otherwise.
• Biopsy or polyp results typically come back within days to a couple of weeks and are reviewed by the doctor.

Risks and When Complications May Be Discussed

Colonoscopy is generally considered safe, but possible risks include:

• Bleeding, especially after a polyp is removed; it can occur up to a couple of weeks later.
• Perforation (a tear in the colon wall), which is rare but serious.
• Reactions to sedation medicine.
• Missed polyps or lesions, which is more likely if the bowel prep was incomplete.
• Severe abdominal pain, fever, or heavy rectal bleeding after a colonoscopy are generally considered reasons to contact a medical professional promptly.

Questions to Ask a Healthcare Professional

General questions people often find useful to bring to an appointment:

• What are the different colorectal cancer screening options, and how do they compare?
• How should the bowel prep be done, and what if it does not seem to be working?
• Which medicines need to be discussed before the procedure?
• What kind of sedation will be used?
• When and how will biopsy or polyp results be shared?
• When might a repeat colonoscopy be recommended?

Sources

This guide was written in plain language from the following authoritative references.

1. Colonoscopy — MedlinePlus (U.S. National Library of Medicine)
2. Colonoscopy — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
3. Colorectal Cancer Screening — MedlinePlus (U.S. National Library of Medicine)

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