Sigmoidoscopy (Anoscopy, Proctoscopy)
Anoscopy, proctoscopy, and sigmoidoscopy tests allow your doctor to look at the inner lining of your anus, your 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 tests use different scopes and look at different sections of the colon.
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). This test can usually be done at any time because it does not require any special preparation (enemas or laxatives) to empty the colon.
During a proctoscopy, a slightly longer scope than the anoscope is used to view the inside of the rectum. You will probably have to use an enema or laxative to empty the colon before the test is done.
- The proctoscope is about 10 in. (25 cm) to 12 in. (32 cm) long and 1 in. (2.5 cm) wide. It allows your doctor 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.
During a sigmoidoscopy, a lighted tube is inserted through the anus. Your doctor can remove small growths and collect tissue samples (biopsy) through a sigmoidoscope. You will have to use an enema or laxative (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 scope allows your doctor to see around bends in the colon.
Flexible sigmoidoscopy is one of many tests that may be used to screen for colon cancer. Which screening test you choose depends on your risk, your preference, and your doctor. Talk to your doctor about what puts you at risk and what test is best for you.
Why It Is Done
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.
How To Prepare
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 doctor to find out if you need to stop taking some medicines, such as aspirin or other blood thinners, before the test.
The preparation for these tests usually involves a thorough cleaning of the lower colon. It must be completely clear of stool (feces). Even a small amount of stool can affect the accuracy of the test.
- You may be told to follow a liquid diet for 1 to 2 days before the test.
- You may be told to not eat for up to 12 hours before the test.
- You may need to have two enemas before the test.
- You may not need special preparation, especially if you have watery or bloody diarrhea.
How It Is Done
You will most likely 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.
When you are in position:
- Your doctor will gently insert a gloved finger into your anus. For men, your doctor 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 doctor can see more clearly.
- Suction may be used to remove watery stool, enema liquid, mucus, or blood through the scope.
- After your doctor has moved the scope forward as far as possible, it is slowly withdrawn while tissue is carefully inspected.
- Your doctor may also insert tiny tools (forceps, loops, swabs) through the scope to collect tissue samples (biopsy) or to remove growths. Tissue samples may be sent to a lab for examination.
After the test
After the scope is removed, your anal area will be cleaned with tissues. If you are having cramps, passing gas may help relieve them.
How long the test takes
The entire examination usually takes 5 to 15 minutes. It may take slightly longer if tissue samples are taken or if polyps are removed.
How It Feels
These tests can be uncomfortable. You may have cramping or a feeling of pressure or bloating. You may feel a brief, sharp pain when the scope is moved forward or when air is blown into your colon. As the scope is moved up the colon, you may feel the need to have a bowel movement and pass gas. If you have pain, tell your doctor.
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.
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. But these problems are rare.
- There is also a slight chance of a colon infection (very rare).
Your doctor should be able to discuss some of the findings with you right after the test. Lab results (such as from a biopsy) may take several days.
Abnormal findings include:
Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.
Current as of: September 8, 2021
Author: Healthwise Staff
Adam Husney MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Arvydas D. Vanagunas MD - Gastroenterology