Flexible Sigmoidoscopy

A flexible sigmoidoscopy is an examination of the lower (distal) part of the gastrointestinal tract, called the colon or large intestine (show figure 1). It is performed by an endoscopist, a doctor or other health professional with special training in endoscopic procedures. In many situations, colonoscopy allows the physician to examine the entire large intestine, and is preferred to flexible sigmoidoscopy if the entire colon needs to be examined.


The most common reasons for flexible sigmoidoscopy are the following:

  • Historically, as a screening test to detect colon polyps or colon cancer in people over age fifty. This recommendation has been replaced by colonoscopy as the primary screening tool.
  • Blood in the stool or rectal bleeding thought to come from the lower colon or anorectal area
  • Persistent diarrhea
  • After radiation treatment to the pelvis when a patient has lower gastrointestinal symptoms
  • For the medical management of colitis (inflammation of the colon)


Our office will provide specific Instructions about how to prepare for the examination. The instructions are designed to maximize safety during and after the examination, minimize possible complications, and allow the endoscopist to easily view the colon.

It is important to read these instructions ahead of time and follow them carefully. Call your clinician or the endoscopy unit if you have questions.

Bowel cleaning
The lower part of the colon must be cleaned to permit the endoscopist to see the inside lining of the colon. Specific instruction will be provided, although preparation usually involves consuming a clear liquid diet, laxatives, and use of an enemas shortly before the examination.

Some medications, such as aspirin products and iron preparations, should be stopped one to two weeks before the examination. Aspirin increases the risk of bleeding after the test, while iron coats the colon, making it difficult to see the lining. People who take a blood thinning medication such as warfarin (Coumadin) or Pradaxa should consult with their clinician regarding the need to stop taking this medication temporarily.

Most medications for high blood pressure, heart disease, lung disease, and seizure disorders are safe during sigmoidoscopy and can be taken the day of the examination.

Medications for diabetes may need to be decreased before the test; patients should talk with their diabetes clinician.


Prior to the sigmoidoscopy, a nurse will ask questions to ensure the patient understands the procedure and the reason it is planned A doctor will review the procedure, including possible complications, and will ask the patient to sign a consent form.


Flexible sigmoidoscopy usually takes between five and fifteen minutes. It is performed while the patient is awake and lies on their left side with the legs curled up against the chest. The sigmoidoscope, which is approximately the size of one finger, is inserted into the anus and advanced through the rectum, sigmoid colon, and descending colon. The sigmoidoscope has a lens and a light source that permits the endoscopist to look into the scope or at a television monitor.

The endoscope allows the endoscopist to take biopsies (small pieces of tissue) and to introduce or withdraw fluid or air. Biopsies do not hurt because the lining of the colon does not sense pain. However, some patients will feel cramping as air is introduced through the scope and as the scope is passed through segments of the colon. The air is needed to permit the endoscopist to advance the scope and see the lining of the colon. It is common to feel embarrassed about releasing air through their rectum, although this is recommended to decrease discomfort. Let the endoscopist know if there is discomfort since air can also be removed through the scope. Because the procedure is brief and discomfort is mild, pain medications or sedation are not routinely used.


Flexible sigmoidoscopy is a safe procedure and complications are rare.

  • Bleeding can occur from biopsies or the removal of polyps, but this is usually minimal and stops quickly or can be controlled.
  • The scope can cause a tear or hole in the tissue being examined. This is a serious problem that does not occur commonly.
  • Lesions can be missed.

After flexible sigmoidoscopy, the following problems should be reported to us immediately:

  • Severe abdominal pain (not just gas cramps)
  • A persistent or increasingly firm, distended abdomen
  • Vomiting
  • Fever
  • Bleeding greater than a few tablespoons


Although patients worry about discomforts of the examination, most people tolerate it very well and feel fine afterwards. Most patients are able to return to normal activities, including eating, after the examination

Patients should contact their doctor about the results of the test and if there are any questions. The endoscopy team will let the patient know when all the results will be available and if further treatment is necessary.