Alternative names
Proctoscopy; Proctosigmoidoscopy


Sigmoidoscopy is an internal examination of the distal large bowel (colon), using an instrument called a sigmoidoscope. The sigmoidoscope is a small camera attched to a flexible tube. It is inserted into the colon to examine the rectum, and the sigmoid and descending portions of the colon.

How the test is performed

During the test, you wear a hospital gown so that the lower half of your body is exposed. You are positioned on your left side with your knees drawn up toward your chest.

A gastroenterologist (a specialist in diseases of the digestive system) will gently insert a gloved and lubricated finger (or fingers) into the rectum to check for blockage and to dilate the anus. This is called a digital rectal examination.

Following the digital rectal exam, the sigmoidoscope will be inserted. This flexible fiberoptic tube is about 20 inches long.

The scope is gently advanced into the colon. Air is introduced into the scope to aid in viewing. The air may cause the urge to defecate. As the sigmoidoscope is slowly removed, the lining of the bowel is carefully examined. A channel in the scope allows for the passage of forceps for biopsies or other instruments for therapy.

How to prepare for the test
You must sign an informed consent form. You will wear a hospital gown.

On the morning of the procedure, eat a light breakfast and then use a cleansing enema about 1 hour before the sigmoidoscopy.

Infants and children:
The preparation you can provide for this test depends on your child’s age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:

How the test will feel

There will be pressure when the scopes or fingers are introduced into your rectum. There will be a feeling of the need to defecate during the procedure. There may be some bloating or cramping from distention of the bowel by air or stretching by the sigmoidoscope. Biopsies cause no discomfort.

After the test, you will expel the air that was introduced.

Why the test is performed

This test can help diagnose:

This test can also be used to:

  • Determine the cause of blood, mucus, or pus in the stool  
  • Confirm findings of another test or X-rays  
  • Take a biopsy of a growth

Normal Values

Normal findings show that the lining of the sigmoid colon, rectal mucosa, rectum, and anus appear normal in color, texture, and size.

What abnormal results mean

Abnormal results can indicate:

  • Hemorrhoids  
  • Anal fissures  
  • Anorectal abscess  
  • Cancer  
  • Colorectal polyps  
  • Inflammation or infection (Proctitis)  
  • Bowel obstruction  
  • Inflammatory bowel disease  
  • Diverticulosis

What the risks are

There is slight risk of bowel perforation (hole) and bleeding at the biopsy sites (the overall risk is approximately 1 out of 1,000).

Johns Hopkins patient information

Last revised: December 8, 2012
by Armen E. Martirosyan, M.D.

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