Flexible sigmoidoscopy (FS) is a medical technique that allows for the visualization of the lining of the gut, specifically the rectum and a part of the colon (up to approximately 60 cm). It is carried out using a sigmoidoscope, a flexible tube approximately the width of a thumb.
It is inserted into the anus and slowly advanced through the rectum and lower part of the colon and has a camera attached to its tip with which images are obtained. Where applicable, biopsies (i.e. tissue samples) may be obtained during the procedure.
Indications for Flexible Sigmoidoscopy
There are a number of reasons why FS may be recommended. Patients with intestinal signs and symptoms, such as bleeding from the anus accompanied by abdominal pain, changes in bowel habits and/or weight loss are prime reasons for the examination. The procedure helps to explore and confirm or disconfirm bowel pathologies that may be associated with these symptoms.
FS may also be used to screen for colon cancer every 5 years after the fifth decade of life. Screening is especially advisable in African American populations because there is a significant incidence of colon cancer in this group of people. Other high risk groups include persons with a family history of colon cancer and existing inflammatory bowel disease.
One limitation of FS is that it does not allow for visualization of the entire colon and cancers that are beyond the reach of the scope may not be detected. Other visualization techniques such as a colonoscopy are the preferred screening method in these cases because the entire colon can be examined. The advantage with FS, however, is that the procedure usually takes less time to prepare and perform.
The entire procedure takes approximately just under a half an hour and the patient does not usually need anesthesia. The scope may be lubricated with gel to allow for easy entry to the anus and is then slowly guided through the rectum and into the sigmoid colon. As the sigmoidoscope is advanced, it inflates the colon with air to optimize visualization of the bowel. The images obtained are sent to a computer screen in real time.
The scope is gradually advanced until it reaches the transverse colon and then the withdrawal process is also down slowly with continued examination of the colon. If any areas of the bowel wall appear suspicious, biopsies are taken for further analysis. Taking a biopsy does not cause any pain or discomfort to the patient. Furthermore, the entire FS itself is usually well-tolerated; however, patients may feel some cramping, pressure or bloating during the procedure.
The sigmoidoscope is designed to allow for the passage of small tools – this allows the specialist to obtain a biopsy or remove polyps. If there is any bleeding that arises as a result of these interventions, an electrical probe or drugs may be administered through the sigmoidoscope to stop it. The discovery of polyps may warrant the need for further examination of the colon with a colonoscopy and other screening tests.
Reviewed by Afsaneh Khetrapal, BSc (Hons)