Flexible 

Sigmoidoscopy 

National Digestive Diseases Information Clearinghouse 

U.S. Department 

of Health and 

Human Services 

NATIONAL 

INSTITUTES 

OF HEALTH 

What is flexible 

sigmoidoscopy? 

Flexible sigmoidoscopy is a procedure used 

to see inside the sigmoid colon and rectum. 

Flexible sigmoidoscopy can detect inflamed 

tissue, abnormal growths, and ulcers. The 

procedure is used to look for early signs of 

cancer and can help doctors diagnose unexplained changes in bowel habits, abdominal 

pain, bleeding from the anus, and weight 

loss. 

What are the sigmoid colon 

and rectum? 

The sigmoid colon is the last one-third of 

the colon. The colon comprises three main 

parts: the ascending colon, the transverse 

colon, and the sigmoid colon—sometimes 

called the descending colon. The colon 

absorbs nutrients and water and forms stool. 

The rectum is about 6 inches long and connects the sigmoid colon to the anus. Stool 

leaves the body through the anus. Muscles 

and nerves in the rectum and anus control 

bowel movements. 

The sigmoid colon is the last one-third of the colon. 

Ascending 

colon 

Sigmoid 

colon 

Transverse 

colon 

Rectum 

Anus 
 

How is flexible 

sigmoidoscopy different 

from colonoscopy? 

Flexible sigmoidoscopy enables the doctor to 

see only the sigmoid colon, whereas colonoscopy allows the doctor to see the entire 

colon. Colonoscopy is the preferred screening method for cancers of the colon and 

rectum; however, to prepare for and perform 

a flexible sigmoidoscopy usually requires less 

time. 

How to Prepare for a 

Flexible Sigmoidoscopy 

To prepare for a flexible sigmoidoscopy, 

one or more enemas are performed about 

2 hours before the procedure to remove all 

solids from the sigmoid colon. An enema 

is performed by flushing water, laxative, or 

sometimes a mild soap solution into the anus 

using a special wash bottle. 

In some cases, the entire gastrointestinal tract must be emptied by following a 

clear liquid diet for 1 to 3 days before the 

procedure—similar to the preparation for 

colonoscopy. 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 also be required 

the night before a flexible sigmoidoscopy. 

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. 

Patients should inform their 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 

2 Flexible Sigmoidoscopy 
 

 

How is a flexible 

sigmoidoscopy performed? 

Examination of the Sigmoid 

Colon 

During a flexible sigmoidoscopy, patients lie 

on their left side on an examination table. 

The doctor inserts a long, flexible, lighted 

tube called a sigmoidoscope, or scope, into 

the anus and slowly guides it through the rectum and into the sigmoid colon. The scope 

inflates the colon with air to give the doctor a 

better view. A small camera mounted on the 

scope transmits a video image from inside 

the colon to a computer screen, allowing the 

doctor to carefully examine the tissues lining 

the sigmoid colon and rectum. The doctor 

may ask the patient to move periodically so 

the scope can be adjusted for better viewing. 

When the scope reaches the transverse colon, 

the scope is slowly withdrawn while the lining 

of the colon is carefully examined again. 

Biopsy and Removal of Colon 

Polyps 

The doctor can remove growths, called 

polyps, during flexible sigmoidoscopy using 

special tools passed through the scope. 

Polyps are common in adults and are usually harmless. However, most colon cancer 

begins as a polyp, so removing polyps early is 

an effective way to prevent cancer. If bleeding occurs, the doctor can usually stop it with 

an electrical probe or special medications 

passed through the scope. 

During a flexible sigmoidoscopy, the doctor 

can also take samples from abnormal-looking 

tissues. Called a biopsy, this procedure 

allows the doctor to later look at the tissue 

with a microscope for signs of disease. 

Tissue removal and the treatments to stop 

bleeding are usually painless. If polyps or 

other abnormal tissues are found, the doctor 

may suggest examining the rest of the colon 

with a colonoscopy. 

Recovery 

A flexible sigmoidoscopy takes about 

20 minutes. Cramping or bloating may occur 

during the first hour after the procedure. 

Bleeding and puncture of the large intestine 

are possible but uncommon complications. 

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 

3 Flexible Sigmoidoscopy 
 

Points to Remember 

•	 Flexible sigmoidoscopy is a procedure used to see inside the sigmoid 

colon and rectum. 

•	 One or more enemas are performed about 2 hours before the 

procedure to remove all solids from 

the sigmoid colon. 

•	 In some cases, the entire gastrointestinal tract must be emptied— 

similar to the preparation for 

colonoscopy. 

•	 A sigmoidoscope transmits a video 

image from inside the colon to a 

computer screen. 

•	 A doctor can biopsy abnormal-


looking tissues during a flexible 


sigmoidoscopy. 


•	 Polyps can be removed using 

special tools passed through the 

sigmoidoscope. 

•	 If polyps or other abnormal tissues 

are found, the doctor may suggest 

examining the rest of the colon 

with a colonoscopy. 

•	 A flexible sigmoidoscopy takes 


about 20 minutes. 


Hope through Research 

The National Institute of Diabetes and 

Digestive and Kidney Diseases conducts 

and supports basic and clinical research into 

many digestive disorders. 

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 Flexible Sigmoidoscopy 
 

 

 

 

 

 

 

 

 

 

 

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 

•	 Colonoscopy 

•	 ERCP (Endoscopic Retrograde 


Cholangiopancreatography)
 

•	 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 Flexible Sigmoidoscopy 
 

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. 09–4332 

November 2008