• Medical Author: Michael J Klevens, MD
  • Coauthor: Jacob W Ufberg, MD
  • Medical Editor: Scott H Plantz, MD, FAAEM
  • Medical Editor: Francisco Talavera, PharmD, PhD
  • Medical Editor: Thomas Rebbecchi, MD, FAAEM

What is a Sigmoidoscopy?

Sigmoidoscopy is a procedure in which a doctor looks in your large intestine. A length of flexible tube connected to a fiberoptic camera is used. A light is transmitted through the scope to the tip by a bundle of light fibers. The doctor uses this light to look at your intestine through an eyepiece or video screen.

  • Your doctor may do this very safe procedure for several reasons.
  • Three findings are possible from this procedure.
    • You are healthy, and no other studies are needed. (Even though the sigmoidoscopy is the most important technique in the evaluation of colon cancer, a very small percentage of people with normal sigmoidoscopy findings may later be found to have colon cancer.)
    • A diagnosis of your particular disease is made.
    • You may need additional testing, consultation, therapy, or follow-up.
  • Several leading medical groups recommend routine screening of men and women aged 50 years and older for colon cancer and benign (harmless) polyps every 3-5 years. Younger people may require this procedure if they have close relatives with colon cancer.
  • A similar screening procedure is known as a colonoscopy. The basic difference is that the tube goes farther up the colon with a colonoscopy.

What Are the Risks of Sigmoidoscopy?

The risks of the procedure include damage to the colon by the tube, bleeding, abdominal pain, and infection.

Sigmoidoscopy Preparation

Sigmoidoscopy is well tolerated by the vast majority of people. This procedure is usually done in a doctor's office without the need for any anesthesia or sedation.

  • Your doctor may require you to use a strong laxative (called a bowel cleanser) to clear your bowel of fecal contents before sigmoidoscopy. Several medications are available for bowel cleansing, including polyethylene glycol 3350 (GoLYTELY, NuLYTELY), magnesium citrate, (Citroma), and senna (X-Prep). These medications produce diarrhea, which can be uncomfortable, but unless the bowel is empty of stool, the test can be limited and may need to be repeated at a later date. Your doctor may also require a special diet, such as a clear liquid diet, starting 1-2 days before your scheduled sigmoidoscopy.
  • Some people also need to use an enema (liquid is forced into the colon through the anus) before bedtime.
  • The next day, you may take your normal medications.
  • About 1 hour before the procedure is to begin, you will need to have an enema. The clear diet and enema help clear the intestine so your doctor can see well.

During the Sigmoidoscopy Procedure

  • The doctor will have you lie down on your left side with your knees bent and pulled up slightly toward your head.
  • The doctor will examine your rectum first with a finger lubricated with special jelly. The tip of the scope is then lubricated with the same jelly and slowly inserted into your rectum.
  • The doctor will slowly advance the tube through your lower intestine. In order to help the doctor see, a small amount of air and water may be placed in the intestine through the end of the scope. If the doctor encounters a suspicious area of intestine, he or she may remove a small piece of the tissue for analysis. This is done with the same scope and is known as a biopsy.
  • The doctor will end the procedure and tell you the outcome of your study.

After the Sigmoidoscopy Procedure

After the procedure, you may experience mild abdominal cramping and gas as a result of the air that was placed in your intestine. Some people may have slight rectal bleeding due to minor irritation and trauma from the insertion of the sigmoidoscope.

When to Seek Medical Care for Sigmoidoscopy Complications

You should notify the doctor if you experience:

  • severe abdominal pain,
  • nausea,
  • vomiting, or
  • heavy bleeding after a sigmoidoscopy.

Your doctor may instruct you to go to the hospital's emergency department if you experience severe abdominal pain, nausea, vomiting, or heavy bleeding after a sigmoidoscopy.

Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


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