Sigmoidoscopy (Anoscopy, Proctoscopy)

	Test Overview
	Health Tools
	Why It Is Done
	How To Prepare
	How It Is Done
	How It Feels
	Risks
	Results
	What Affects the Test
	What To Think About
	References
	Credits

Anoscopy, proctoscopy, and sigmoidoscopy tests allow your health professional to look at the inner lining of your anus, rectum, and the lower part of the large intestine (colon). These tests are used to look for abnormal growths (such as tumors or polyps), inflammation, bleeding, hemorrhoids, and other conditions (such as diverticulosis).

These test use different scopes look at different sections of the colon.

• Anoscopy. During an anoscopy, a short, rigid, hollow tube (anoscope) that may contain a light source is used to look at the last 2 in. (5 cm) of the colon (anal canal). Anoscopy can usually be done at any time because it does not require any special preparation (enemas or laxatives) to empty the colon.
• Proctoscopy. During a proctoscopy, a slightly longer instrument than the anoscope is used to view the inside of the rectum. You usually will have to use enemas or laxatives to empty the colon before the test is done.
• Sigmoidoscopy. During a sigmoidoscopy, a lighted tube that may be either rigid or flexible is inserted through the anus. Your health professional can remove small growths and collect tissue samples (biopsy) through a sigmoidoscope. You will have to use enemas or laxatives (or both) to empty the colon before the test is done.
  • The flexible sigmoidoscope is about 2.3 ft (70 cm) long and 0.5 in. (1 cm) wide with a lighted lens system. This instrument allows your health professional to see around bends in the colon. A flexible sigmoidoscope allows a more complete view of the lower colon than a rigid scope and usually makes the examination more comfortable. The flexible sigmoidoscope generally has replaced the rigid sigmoidoscope.
  • The rigid sigmoidoscope is used less often. It is about 10 in. (25 cm) to 12 in. (32 cm) long and 1 in. (2.5 cm) wide. It allows your health professional to look into the rectum and the bottom part of the colon, but it does not reach as far into the colon as the flexible sigmoidoscope.

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	Which test should I have to screen for colorectal cancer?

These tests are done to:

• Detect problems or diseases of the anus, rectum, or lower large intestine (sigmoid colon). These tests are often done to investigate symptoms such as unexplained bleeding from the rectum, long-lasting diarrhea or constipation, blood or pus in the stool, or lower abdominal pain.
• Remove polyps or hemorrhoids.
• Monitor the growth of polyps or the treatment of inflammatory bowel disease.
• Screen for colon cancer or polyps.

Anoscopy

Usually, no preparation is needed for an anoscopy.

Proctoscopy and sigmoidoscopy

Test preparation for a proctoscopy and sigmoidoscopy may be similar. Before the test:

• Talk with your health professional to find out if you need to stop taking some medicines, such as warfarin, before the test.
• Talk with your health professional to find out if you need to take antibiotics before the test, especially if you have a heart murmur, an artificial heart valve, or an artificial implant (such as a replacement joint).
• Tell your health professional if you have been diagnosed with peritonitis, diverticulitis, or toxic megacolon or if you have had recent bowel surgery.

The preparation for these tests usually involves a thorough cleaning of the lower colon, because it must be completely clear of stool (feces). Even a small amount of fecal material can affect the accuracy of the test.

• You may be instructed to follow a liquid diet for 1 to 2 days before the test.
• You may be instructed to not eat for up to 12 hours before the test.
• You may need to have an enema the night before the test and another enema an hour before the examination.
• You may not need special preparation, especially if you have watery or bloody diarrhea.

Talk to your health professional about any concerns you have regarding the need for this test, its risks, how it will be done, or what the results may indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

You will usually lie on your left side during the test. You may also be asked to kneel on the table with your bottom raised in the air.

Once you are in position:

• Your health professional will gently insert a gloved finger into your anus to check for tenderness or blockage. For men, your health professional will also check the condition of the prostate gland.
• The lubricated scope is then inserted. The scope is moved slowly forward into the rectum and lower colon. During a sigmoidoscopy, puffs of air sometimes are blown through the scope to open the colon so that your health professional can see more clearly.
• Suction may be used to remove watery stool, enema liquid, mucus, or blood through the scope.
• Once your health professional has moved the scope forward as far as possible, it is slowly withdrawn while tissue is carefully inspected.
• Your health professional may also insert tiny instruments (forceps, loops, swabs) through the scope to collect tissue samples (biopsy) or to remove growths. Tissue samples may be sent to a laboratory for examination.

See the following pictures:

• Step 1: The sigmoidoscope is inserted.
• Step 2: The health professional examines the wall of the sigmoid colon.

After the scope is removed, your anal area will be cleaned with tissues. If you are having cramps, passing gas may help relieve them.

The entire examination usually takes 5 to 15 minutes, slightly longer if tissue samples are taken or if polyps are removed.

If you received a sedative during the test, do not drive, operate machinery, or sign legal documents for 24 hours after the test. Arrange to have someone drive you home after the test.

After the test you may resume your regular diet, unless your health professional gives you other directions. Be sure to drink plenty of liquids to replace those you have lost during the preparation for the sigmoidoscopy.

An anoscopy, proctoscopy, and sigmoidoscopy examination can be embarrassing and uncomfortable. You may have cramping, a feeling of pressure or bloating, or feel a brief, sharp pain when the scope is moved forward or when air is blown into your colon.

The removal of tissue samples (biopsy) from the colon does not cause discomfort. A local anesthetic is used when a biopsy of the anal area is done. Your anus may be sore for a few days.

You may have mild gas pains and may need to pass some gas after the procedure. Walking may help relieve the gas pains.

If a biopsy was done or a polyp removed, you may have traces of blood in your stool for a few days.

There is very little risk of complications from having an anoscopy, proctoscopy, or sigmoidoscopy.

• There is a slight chance of piercing the colon (perforation) or causing severe bleeding by damaging the wall of the colon. However, these problems are rare.
• There is also a slight chance of a colon infection (very rare).

Call your health professional immediately if you have:

• Heavy rectal bleeding.
• Severe abdominal pain.
• A fever.

Anoscopy, proctoscopy, and sigmoidoscopy tests allow your health professional to look at the inner lining of your anus, rectum, and the lower part of the large intestine (colon).

Your health professional should be able to discuss some of the findings with you immediately after the test. Lab results (such as from a biopsy) may take several days.

Your health professional will discuss any significant abnormal results with you in relation to your symptoms and past health.

Factors that can interfere with your test or the accuracy of the results include:

• Stool in the colon or rectum.
• The structure of the colon, such as a colon that has many turns.
• A barium enema done within a week before sigmoidoscopy.
• Rectal bleeding.

• Follow-up tests, such as colonoscopy, may be needed after sigmoidoscopy. A colonoscopy may also be needed to examine the upper section of the colon if growths were seen during sigmoidoscopy. For more information, see the medical test Colonoscopy.
• In some cases, the sigmoidoscope may be attached to a video monitor and a recording device that lets your health professional see the inside the colon and record the findings.
• Most medical experts recommend colon cancer screening beginning at age 50 for people who have an average risk and earlier for those who have an increased risk for colon cancer, such as those with a family history of colon cancer. Talk with your health professional about which colon cancer screening test is best for you.
• You may not be able to have this test if you have peritonitis, diverticulitis, toxic megacolon, or if you have had recent bowel surgery.

For more information on screening tests for colon cancer, see:

Which test should I have to screen for colon cancer?

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2002). Mosby’s Manual of Diagnostic and Laboratory Tests, 2nd ed. St. Louis: Mosby.