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Definition: An internal examination of the rectum, distal sigmoid colon, and large bowel using a type of small camera (flexible sigmoidoscope).

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.

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

Following the digital rectal exam, the sigmoidoscope will be inserted. This is a flexible fiberoptic tube 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.


A sample of colon tissue is obtained during a colonoscopy procedure using special instruments. The specimen is sent to the laboratory and placed in a culture media. The specimen is examined daily for the presence of microorganisms.

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.

How the test will feel: The sedative and pain medication will provide relaxation and produce a drowsy feeling. A rectal examination usually precedes the test to dilate the rectum and make sure there are no major obstructions. You may have the urge to defecate when the rectal exam is performed or as the colonoscope is inserted.

You may feel pressure as the scope moves inside. Brief cramping and gas pains may be experienced as air is inserted or as the scope advances. The passing of gas is necessary and should be expected.

Discomfort may be lessened by taking slow, deep breaths. This will also help relax the abdominal muscles. Mild abdominal cramping and considerable passing of gas may occur after the exam. Medications will produce sedation, which should wear off in a few hours.

Why the test is performed:

  • to obtain tissue specimen for biopsy
  • to evaluate unexplained blood in the stool, abdominal pain, persistent diarrhea, or abnormalities (such as polyps) found on contrast X-rays (barium enema)
  • to determine the type and extent of inflammatory bowel disease (ulcerative colitis and Crohn's disease)
  • to follow people with previous polyps, colon cancer, or a family history of colon cancer

Normal Values: Normal findings are simply healthy intestinal tissues.

What abnormal results mean:

  • lower gastrointestinal (GI) bleeding
  • polyps (which can be removed through the colonoscope during the exam)
  • tumor
  • inflammatory bowel disease
  • diverticulosis (particularly in older people)

Additional conditions under which the test may be performed:

  • CMV gastroenteritis/colitis
  • colon cancer screening
  • colorectal polyps
  • ischemic colitis
  • pseudomembranous colitis

What the risks are:

  • bowel perforation, requiring an operation to repair the hole (less than 2 out of 1,000 tests)
  • heavy or persistent bleeding from biopsy or polypectomy sites (1 out of 1,000 tests)
  • adverse reaction to sedative medication causing respiratory depression or low blood pressure (4 out of 10,000 tests)
  • infection requiring antibiotic therapy (very rare)
  • nausea, vomiting, bloating, and rectal irritation caused by oral purgatives

Special considerations: You must sign an informed consent form. Several hours rest is recommended after the test. To replace fluids lost because of laxatives and fasting, drink plenty of liquids after the test.

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