(Flexible Sigmoidoscopy, Proctosigmoidoscopy, Proctoscopy, Anoscopy)

Procedure overview

What is a sigmoidoscopy?

A sigmoidoscopy is a diagnostic procedure that allows the doctor to examine the lower one-third of the large intestine. Sigmoidoscopy is helpful in identifying the causes of diarrhea, abdominal pain, constipation, abnormal growths, and bleeding. It may also be used to obtain biopsies and to perform procedures such as removal of polyps or hemorrhoids. Sigmoidoscopy is also used to screen for colorectal cancer, the second leading cause of cancer deaths in the U.S.

A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum into the lower part of the large intestine. Air is injected into the intestine through the sigmoidoscope to inflate it for better viewing.

Several procedures may be used to examine different portions of the large intestine. These include a colonoscopy (examination of the entire length of the large intestine), proctoscopy (examination of the anus and rectum), and anoscopy (examination of the anus only). Please see these procedures foe additional information.

Although less invasive X-ray procedures, such as a barium enema, may be used to evaluate the large intestine, these procedures cannot provide the direct visualization of the internal intestine necessary to evaluate and diagnose certain conditions.

Anatomy of the colon

Illustration of the anatomy of the digestive system, adult
Click Image to Enlarge

The large intestine, or colon, has four sections:

The rectum joins the anus, or the opening where waste matter passes out of the body.

Screening guidelines for colorectal cancer

Colorectal cancer screening guidelines for early detection from the American Cancer Society recommend that beginning at age 50, both men and women should follow one of the examination schedules below:

Persons with any of the following colorectal cancer risk factors should begin screening procedures at an earlier age and be screened more often:

Reasons for the procedure

A sigmoidoscopy may be used to visualize or diagnose colon polyps, tumors, ulceration, inflammation, hemorrhoids, diverticula (pouches), and strictures (narrowing) in the sigmoid colon. It may also be used to determine the cause of recent changes in bowel habits, lower abdominal pain, itching around the anus, or the passage of blood or mucus in the stool.

There may be other reasons for your doctor to recommend a sigmoidoscopy.

Risks of the procedure

As with any invasive procedure, complications may occur. Complications related to sigmoidoscopy may include, but are not limited to, the following:

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

Certain factors or conditions may interfere with a sigmoidoscopy. These factors include, but are not limited to, the following:

Before the procedure

During the procedure

A sigmoidoscopy may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.

Generally, the sigmoidoscopy follows this process:

  1. You will be asked to remove any jewelry or other objects that may interfere with the procedure.
  2. You will be asked to remove clothing and be given a gown to wear.
  3. You will be asked to lie on the procedure table on your left side with your knees bent towards your chest. Alternatively, you may be positioned in the knee-chest position, on your knees with your head and chest bent down, touching the table.
  4. The doctor will conduct a rectal exam to check for the presence of blood, mucus, or fecal matter and to help dilate the anus.
  5. A lubricated sigmoidoscope will be slowly inserted into the anus and advanced into the rectum and lower part of the colon (distal sigmoid colon). After the sigmoid colon is visualized, the sigmoidoscope will be removed.
  6. Sigmoidoscopy may be performed in conjunction with an anoscopy and/or a proctoscopy. If these procedures are performed, an anoscope and/or a proctoscope will be inserted to visualize the lower rectum and/or anal canal.
  7. Although minimal discomfort is associated with the procedure, you may feel a strong urge to have a bowel movement when the sigmoidoscope is inserted. You may also feel temporary muscle spasms or lower abdominal pain during the procedure. Taking deep breaths while the tube is being inserted may help to help decrease the discomfort.
  8. Air may be introduced into the bowel to aid visualization. A suction device may be used to remove liquid feces.
  9. During the procedure, specimens and/or biopsies (tissue samples) may be taken from the lining of the large intestine with a special brush, forceps, or swab.
  10. If a polyp is seen, it may be removed, biopsied, or left alone until a subsequent operation is performed.
  11. After the procedure is completed, the instrument will be removed.

After the procedure

If you were positioned in the knee-chest position during the procedure, you should lie on your side or back for a few minutes before getting up from the table. You should move slowly when standing up in order to avoid dizziness from having your head down during the procedure.

You may resume your normal diet and activities, unless otherwise instructed.

If a biopsy or polyp removal was done during the procedure, you may notice a small amount of blood in your bowel movement. This bleeding should stop within a day or so.

You may experience excessive flatulence (passing of gas) and gas pains after the procedure. This is normal. Walking and moving about may help to ease any discomfort.

Notify your physician to report any of the following:

Following a sigmoidoscopy, your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

Online resources

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.

This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, nor do these sites endorse the information contained here.

American Cancer Society

American College of Gastroenterology

American Gastroenterological Association

National Cancer Institute (NCI)

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

National Institutes of Health (NIH)

National Library of Medicine


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