Sigmoidoscopy
Sigmoidoscopy, also known as proctosigmoidoscopy, is a medical procedure that involves the insertion of a lighted tube called a sigmoidoscope through the anus to examine the lining of the rectum and lower colon. This procedure is primarily used for screening and diagnosing conditions such as sigmoid colon and rectal cancer, as well as for follow-up evaluations after surgery. Unlike colonoscopy, sigmoidoscopy is less invasive and allows doctors to view only a portion of the colon.
Patients typically prepare for the procedure by cleansing the rectum and lower colon, often with an enema, and may need to stop certain medications beforehand. During the procedure, which is usually performed in an outpatient setting, the patient remains awake while the physician examines the colon and rectum for abnormalities, with the option for sedation if needed. Risks are minimal but can include perforation, bleeding, and infection. After the examination, any abnormal growths can be sampled, treated, or monitored, with results helping to determine the appropriate next steps. Due to its limited view compared to colonoscopy, individuals opting for sigmoidoscopy may be advised to undergo the procedure more frequently.
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Sigmoidoscopy
ALSO KNOWN AS: Proctosigmoidoscopy
DEFINITION: Sigmoidoscopy is the insertion of a slender, lighted tube (sigmoidoscope) through the anus to examine the lining of the rectum and lower colon. Sigmoidoscopes vary in insertion tube design (such as size, flexibility, and viewing angle), viewing technology (lens, fiber-optic, or electronic), and procedural capabilities (sample, destroy, remove, or treat abnormalities).
Cancers diagnosed: Sigmoid colon cancer, rectal cancer
Why performed: For cancer, sigmoidoscopy may be performed as a screening procedure to detect abnormalities in the rectum and lower colon; as a diagnostic procedure to determine the cause of symptoms, confirm other findings, or plan treatment; or as a follow-up procedure to verify that tissues healed properly after surgery. Sigmoidoscopy is an alternative to colonoscopy and less invasive; however, it only allows doctors to see a portion of the colon.
Patient preparation: A few days before the procedure, the patient may need to stop certain medications (such as aspirin products and blood thinners). On the day of the procedure, the patient cleanses their rectum and lower colon (such as with an enema).
Steps of the procedure: Sigmoidoscopy is scheduled in a physician’s office or other outpatient setting. The patient wears a gown and lies on the side, awake; if needed, sedation or local anesthetic may be given. First, the physician performs a digital rectal exam. The sigmoidoscope (.25 to .5 inches wide, 10 to 26 inches long) is lubricated and carefully inserted through the anus. Puffs of air gently expand the rectum and lower colon as the physician advances the sigmoidoscope, steering around bends until the sigmoidoscope is fully inserted. The physician slowly withdraws the sigmoidoscope, carefully viewing the lining for abnormalities. When an abnormality is found, its location and characteristics are recorded. Depending on the abnormality, it may be sampled (biopsied), destroyed (ablated), removed (excised and retrieved), or otherwise treated. All samples and excised tissues are taken to the laboratory for histopathologic evaluation.
After the procedure: The patient leaves and resumes normal activities, unless sedation or anesthetic was needed. The patient may feel bloated and have cramps until the extra air passes.
Risks: Sigmoidoscopy is relatively safe, with a small risk for these side effects: perforation, bleeding, infection, irritation, and discharge.
Results: A normal bowel has smooth folds lining the muscular wall, with an even distribution of blood vessels. Abnormalities include inflammation, stricture, vascular changes, anatomic distortions, and abnormal growths, such as mucosal growths, polypoid lesions (polyps), and cancer. Histopathologic evaluation determines whether an abnormal growth is or is not likely to become cancerous and, if the abnormal growth was removed, whether the diseased tissue was completely removed. Additional treatment, follow-up examinations, or both may be recommended. Because sigmoidoscopy shows a smaller portion of the colon in relation to colonoscopy, it is recommended patients receive one on a more frequent basis if it is their choice of diagnostic option.
Bibliography
Adebogun, Akeem O., Christine D. Berg, and Adeyinka O. Laiyemo. "Concerns and Challenges in Flexible Sigmoidoscopy Screening." Colorectal Cancer, vol. 1.4, 2012, pp. 309–19.
Ahmad, Nasir Zaheer, and Aftab Ahmed. "Rigid or Flexible Sigmoidoscopy in Colorectal Clinics? Appraisal Through a Systematic Review and Meta-Analysis." Journal of Laparoendoscopic & Advanced Surgical Techniques, vol. 22.5, 2012, pp. 479–87.
Anderson, Joseph C., and Charles J. Kahi, eds. Colorectal Cancer Screening. New York: Humana-Springer, 2011.
“Flexible Sigmoidoscopy.” Mayo Clinic, 5 Mar. 2022, www.mayoclinic.org/tests-procedures/flexible-sigmoidoscopy/about/pac-20394189. Accessed 17 June 2024.
Haycock, Adam, et al. Cotton and Williams' Practical Gastrointestinal Endoscopy: The Fundamentals. 7th ed. Hoboken: Wiley, 2014.
Schoen, Robert E., et al. "Colorectal-Cancer Incidence and Mortality with Screening Flexible Sigmoidoscopy." New England Journal of Medicine, vol. 366.25, 2012, pp. 2345–57.