A sigmoidoscopy is an internal exam of the lower part of the large intestine (colon) using a short, thin, flexible lighted tube. The tube, called a flexible sigmoidoscope, has a tiny camera at the tip allowing the doctor to view the inside of the rectum and the sigmoid colon—about the last two feet of the large intestine. A small biopsy instrument to remove tissue samples to be checked under a microscope for signs of disease can be performed during the examination.
A flexible sigmoidoscopy can help your doctor determine the cause of abdominal pain, rectal bleeding, changes in bowel habits, chronic diarrhea and other intestinal problems. Your doctor may be able to diagnose the cause of diarrhea, bowel obstruction, diverticulosis, inflammatory bowel disease, anal fissures and hemorrhoids, as well as find colon polyps that might be in this lower part of the colon.
Flexible sigmoidoscopy does not allow the doctor to see the entire colon. Therefore, any cancers or polyps farther into the colon cannot be detected with flexible sigmoidoscopy. A colonoscopy allows the doctor to examine the entire colon.
The lower colon and rectum must be completely empty for a flexible sigmoidoscopy to be thorough and safe. Some doctors recommend a combination of a laxative and a small enema before the test. Some doctors may advise the patient to drink only clear liquids for 12 to 24 hours before the procedure is scheduled. A liquid diet means clear; fat-free bouillon or broth; gelatin; strained fruit juice (no grape juice or any liquid with red color); water; plain, unsweetened coffee or tea; or diet soda. The night before, or even immediately before the flexible sigmoidoscopy, the patient may be given an enema, which is a liquid solution that washes out the lower intestine.
During the test the patient is positioned on the left side with knees drawn up toward the chest. First, the doctor will do a digital rectal exam by gently inserting a gloved and lubricated finger into the rectum to check for any abnormalities.
Next, the sigmoidoscope is inserted into the rectum, and the patient will feel some pressure. Air is introduced through the scope to expand the colon and help the doctor see adequately. As the scope is slowly removed, the lining of the bowel is carefully examined. A hollow channel in the center of the scope allows for the passage of an instrument called a forceps for obtaining a biopsy if needed.
This procedure takes about 15 minutes. After the exam, you may have mild abdominal discomfort. You may feel bloated or pass gas for a few hours as you clear the air from your colon. You will be able to return to your normal diet and routine after the procedure.
You may have a small amount of blood in your stool with your first bowel movement after the procedure. This is normal. Call your doctor if this continues or you have persistent abdominal pain or a fever of 100 degrees Fahrenheit or higher.
What Are the Possible Outcomes of a Flexible Sigmoidoscopy?
You and your doctor will discuss the results of your flexible sigmoidoscopy. The exam is considered negative if the doctor does not find any abnormalities. A positive exam might identify polyps or abnormal issue in the colon. Depending on the findings, you may need additional testing, such as a colonoscopy, so that the entire colon can be examined.