Flexible sigmoidoscopy can find and remove polyps in the rectum and the lower third of the colon. When polyps are found during a flexible sigmoidoscopy, a full colonoscopy is necessary to see if there are more polyps or cancer higher in the colon.
During the exam, a thin, flexible lighted tube about two feet long (sigmoidoscope) is inserted carefully through the anus and into the rectum and lower part of the colon. Air is also blown gently into the intestinal tract so the doctor can see the intestinal lining more clearly.
Image courtesy of the National Cancer Institute
Polyps can be snared and removed through the sigmoidoscope and samples of polyps or other suspicious areas can be biopsied for study by a pathologist.
The lower part of the colon must be clear of stool before the test so preparation may include clear liquids, enemas, or laxatives. Your doctor will give you specific instructions.
Sedation is not used for sigmoidoscopies so they may be uncomfortable, particularly while air is infused. You may feel cramping during the procedure and be bloated afterwards until the air is expelled. Walking may help to get rid of the gas.
Sigmoidoscopies can be done by family physicians or specially-trained nurse practitioners or physician assistants.
Combination Flexible Sigmoidoscopy and FOBT/FIT
Although it is uncertain whether or not combining the two tests results in better screening outcomes, FOBT may find bleeding in polyps or cancers in the right colon beyond the reach of the sigmoidoscope. FOBT or FIT is done annually with sigmoidoscopy added every five years. In the years when both tests are done, FOBT should be completed first since bleeding found on FOBT would lead to colonoscopy and there would be no need for sigmoidoscopy.
Where Can You Go for More Information?
The Mayo Clinic has detailed information on flexible sigmoidoscopy.
The American Society for Gastrointestinal Endoscopy has information for patients on its website, including flexible sigmoidoscopy.
The National Digestive Disease Clearinghouse (part of NIH) includes information on flexible sigmoidoscopy.