Colonoscopy
 National Digestive Diseases Information Clearinghouse 

U.S. Department 

of Health and 

Human Services 

NATIONAL 

INSTITUTES 

OF HEALTH 

What is colonoscopy? 

Colonoscopy is a procedure used to see 

inside the colon and rectum. Colonoscopy 

can detect inflamed tissue, ulcers, and abnormal growths. The procedure is used to look 

for early signs of colorectal cancer and can 

help doctors diagnose unexplained changes 

in bowel habits, abdominal pain, bleeding 

from the anus, and weight loss. 

What are the colon and 

rectum? 

The colon and rectum are the two main parts 

of the large intestine. Although the colon is 

only one part of the large intestine, because 

most of the large intestine consists of colon, 

the two terms are often used interchangeably. The large intestine is also sometimes 

called the large bowel. 

Digestive waste enters the colon from the 

small intestine as a semisolid. As waste 

moves toward the anus, the colon removes 

moisture and forms stool. The rectum is 

about 6 inches long and connects the colon 

to the anus. Stool leaves the body through 

the anus. Muscles and nerves in the rectum 

and anus control bowel movements. 

How to Prepare for 

Colonoscopy 

The doctor usually provides written instructions about how to prepare for colonoscopy. 

The process is called a bowel prep. Generally, 

all solids must be emptied from the gastrointestinal tract by following a clear liquid diet 

Liver 

Small 

intestine 

Colon 

(shaded) 

Stomach 

Rectum 

Anus 

The colon and rectum are the two main parts of the 

large intestine. 

for 1 to 3 days before the procedure. Patients 

should not drink beverages containing red or 

purple dye. Acceptable liquids include 

• fat-free bouillon or broth 

• strained fruit juice 

• water 

• plain coffee 

• plain tea 

• sports drinks, such as Gatorade 

• gelatin 
A laxative or an enema may be required the 

night before colonoscopy. A laxative is medicine that loosens stool and increases bowel 

movements. Laxatives are usually swallowed 

in pill form or as a powder dissolved in water. 

An enema is performed by fl ushing water, 

or sometimes a mild soap solution, into the 

anus using a special wash bottle. 

Patients should inform the doctor of all 

medical conditions and any medications, 

vitamins, or supplements taken regularly, 

including 

• aspirin 

• arthritis medications 

• blood thinners 

• diabetes medications 

• vitamins that contain iron 

Driving is not permitted for 12 hours after 

colonoscopy to allow the sedative time to 

wear off. Before the appointment, patients 

should make plans for a ride home. 

How is colonoscopy 

performed? 

Examination of the Large 

Intestine 

During colonoscopy, patients lie on their left 

side on an examination table. In most cases, 

a light sedative, and possibly pain medication, helps keep patients relaxed. Deeper 

sedation may be required in some cases. The 

doctor and medical staff monitor vital signs 

and attempt to make patients as comfortable 

as possible. 

During colonoscopy, patients lie on their left side on 

an examination table. 

The doctor inserts a long, fl exible, lighted 

tube called a colonoscope, or scope, into the 

anus and slowly guides it through the rectum 

and into the colon. The scope infl ates the 

large intestine with carbon dioxide gas 

to give the doctor a better view. A small 

camera mounted on the scope transmits a 

video image from inside the large intestine 

to a computer screen, allowing the doctor 

to carefully examine the intestinal lining. 

The doctor may ask the patient to move 

periodically so the scope can be adjusted for 

better viewing. 

Once the scope has reached the opening to 

the small intestine, it is slowly withdrawn and 

the lining of the large intestine is carefully 

examined again. Bleeding and puncture of 

the large intestine are possible but uncommon complications of colonoscopy. 

2 Colonoscopy 
Removal of Polyps and Biopsy 

A doctor can remove growths, called polyps, 

during colonoscopy and later test them in 

a laboratory for signs of cancer. Polyps are 

common in adults and are usually harmless. 

However, most colorectal cancer begins 

as a polyp, so removing polyps early is an 

effective way to prevent cancer. 

The doctor can also take samples from 

abnormal-looking tissues during colonoscopy. The procedure, called a biopsy, allows 

the doctor to later look at the tissue with a 

microscope for signs of disease. 

The doctor removes polyps and takes biopsy 

tissue using tiny tools passed through the 

scope. If bleeding occurs, the doctor can 

usually stop it with an electrical probe or special medications passed through the scope. 

Tissue removal and the treatments to stop 

bleeding are usually painless. 

Recovery 

Colonoscopy usually takes 30 to 60 minutes. 

Cramping or bloating may occur during the 

first hour after the procedure. The sedative 

takes time to completely wear off. Patients 

may need to remain at the clinic for 1 to 

2 hours after the procedure. Full recovery is 

expected by the next day. Discharge instructions should be carefully read and followed. 

Patients who develop any of these rare 

side effects should contact their doctor 

immediately: 

• severe abdominal pain 

• fever 

• bloody bowel movements 

• dizziness 

• weakness 

At what age should routine 

colonoscopy begin? 

Routine colonoscopy to look for early signs 

of cancer should begin at age 50 for most 

people—earlier if there is a family history 

of colorectal cancer, a personal history of 

inflammatory bowel disease, or other risk 

factors. The doctor can advise patients about 

how often to get a colonoscopy. 

3 Colonoscopy 
Points to Remember 

• 	 Colonoscopy is a procedure used to 

see inside the colon and rectum. 

• 	 All solids must be emptied from 

the gastrointestinal tract by following a clear liquid diet for 1 to 

3 days before colonoscopy. 

• 	 During colonoscopy, a sedative, 

and possibly pain medication, helps 

keep patients relaxed. 

• 	 A doctor can remove polyps and 

biopsy abnormal-looking tissues 

during colonoscopy. 

• 	 Driving is not permitted for 

12 hours after colonoscopy to allow 

the sedative time to wear off. 

Hope through Research 

The National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK) 

conducts and supports basic and clinical 

research into many digestive disorders. The 

NIDDK is working to improve colonoscopy 

by developing new tools, including tools that 

improve the ability to detect all colon polyps 

and to identify people at increased risk of 

colorectal cancer. Such tools will help train 

doctors to perform colonoscopy, improve 

safety, and make the procedure more comfortable for patients. 

Participants in clinical trials can play a more 

active role in their own health care, gain 

access to new research treatments before 

they are widely available, and help others 

by contributing to medical research. For 

information about current studies, visit 

www.ClinicalTrials.gov. 

4 	 Colonoscopy 
For More Information 

Fact sheets about other diagnostic tests 

are available from the National Digestive 

Diseases Information Clearinghouse at 

www.digestive.niddk.nih.gov, including 

• 	 ERCP (Endoscopic Retrograde 


Cholangiopancreatography)
 

• 	 Flexible Sigmoidoscopy 

• 	 Lower GI Series 

• 	 Liver Biopsy 

• 	 Upper GI Series 

• 	 Upper GI Endoscopy 

• 	 Virtual Colonoscopy 

American College of Gastroenterology 

P.O. Box 342260 

Bethesda, MD 20827–2260 

Phone: 301–263–9000 

Fax: 301–263–9025 

Email: info@acg.gi.org 

Internet: www.acg.gi.org 

American Society for Gastrointestinal 

Endoscopy 

1520 Kensington Road, Suite 202 

Oak Brook, IL 60523 

Phone: 1–866–353–ASGE (2743) 

Fax: 630–573–0691 

Email: info@asge.org 

Internet: www.asge.org 

International Foundation for Functional 

Gastrointestinal Disorders 

P.O. Box 170864 

Milwaukee, WI 53217–8076 

Phone: 1–888–964–2001 or 414–964–1799 

Fax: 414–964–7176 

Email: iffgd@iffgd.org 

Internet: www.iffgd.org 

You may also find additional information about this 

topic by 

• searching the NIDDK Reference Collection at 

www.catalog.niddk.nih.gov/resources 

• visiting MedlinePlus at www.medlineplus.gov 

This publication may contain information about medications. When prepared, this publication included 

the most current information available. For updates 

or for questions about any medications, contact 

the U.S. Food and Drug Administration toll-free at 

1–888–INFO–FDA (463–6332) or visit www.fda.gov. 

Consult your doctor for more information. 

The U.S. Government does not endorse or favor any 

specific commercial product or company. Trade, 

proprietary, or company names appearing in this 

document are used only because they are considered 

necessary in the context of the information provided. 

If a product is not mentioned, the omission does not 

mean or imply that the product is unsatisfactory. 

5 	 Colonoscopy 
National Digestive Diseases 

Information Clearinghouse 

2 Information Way
 

Bethesda, MD 20892–3570
 

Phone: 1–800–891–5389
 

TTY: 1–866–569–1162
 

Fax: 703–738–4929
 

Email: nddic@info.niddk.nih.gov
 

Internet: www.digestive.niddk.nih.gov
 

The National Digestive Diseases Information 

Clearinghouse (NDDIC) is a service of the 

National Institute of Diabetes and Digestive 

and Kidney Diseases (NIDDK). The NIDDK 

is part of the National Institutes of Health of 

the U.S. Department of Health and Human 

Services. Established in 1980, the Clearinghouse 

provides information about digestive diseases 

to people with digestive disorders and to their 

families, health care professionals, and the 

public. The NDDIC answers inquiries, develops 

and distributes publications, and works closely 

with professional and patient organizations and 

Government agencies to coordinate resources 

about digestive diseases. 

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists and 

outside experts. This publication was reviewed 

by Michael Wallace, M.D., Mayo Clinic. 

This publication is not copyrighted. The Clearinghouse 

encourages users of this fact sheet to duplicate and 

distribute as many copies as desired. 

This fact sheet is also available at 

www.digestive.niddk.nih.gov. 

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 09–4331 

November 2008