Colon Cancer Screening (cont.)
Dennis Lee, MD
Dr. Lee was born in Shanghai, China, and received his college and medical training in the United States. He is fluent in English and three Chinese dialects. He graduated with chemistry departmental honors from Harvey Mudd College. He was appointed president of AOA society at UCLA School of Medicine. He underwent internal medicine residency and gastroenterology fellowship training at Cedars Sinai Medical Center.
In this Article
- Introduction to colon cancer screening and surveillance
- Screening recommendations for individuals with average risk of colon cancer
- Fecal occult blood tests
- Flexible sigmoidoscopy
- Screening colonoscopy
- Virtual colonoscopy
- Air contrast (double contrast) barium enema
- Surveillance recommendations for individuals with higher-than-average risk of colon cancer
- Patients with history of colon polyps
- Patients with history of colorectal cancer
- Patients with ulcerative colitis
- Family history of colorectal cancer
- What are hereditary colon cancer syndromes?
- Who should consider genetic counseling and testing and how is it conducted?
- Summary of colon cancer screening
Flexible sigmoidoscopy utilizes a flexible sigmoidoscope, a flexible, fiberoptic viewing tube with a light at the tip. It is inserted through the anus and is used by the doctor to examine the rectum and the part of the colon adjacent to the rectum. It is a shorter version of a colonoscope. Approximately 50% of colorectal cancers and polyps are found to be within the reach of a flexible sigmoidoscope. It is recommended that individuals of average risk for colon cancer undergo a flexible sigmoidoscopy examination at age 50 and every 3-5 years thereafter. If polyps are found during a flexible sigmoidoscopic examination, a colonoscopy to examine the entire colon is recommended to remove the polyps as well as to find and remove additional polyps in other parts of the colon. The removed polyps are examined by a pathologist under a microscope to determine if the polyps are benign, malignant or pre-cancerous. Individuals with precancerous polyps (adenomas and villous adenomas) have a higher than average risk of developing colon cancer, and it is recommended that they return periodically for surveillance colonoscopies (see below). For more information about this procedure, please see the Flexible Sigmoidoscopy article.
Many doctors in the US are recommending screening colonoscopies rather than flexible sigmoidoscopies for healthy subjects with an average risk for developing colon cancer. Colonoscopies are recommended beginning at the age of 50 and thereafter every 7-10 years if no colon polyps or cancers are found. The rationale for this recommendation is:
- Colonoscopy examines the entire colon while flexible sigmoidoscopy only examines the rectum and the colon adjacent to the rectum.
- Approximately half of colon polyps (and colon cancers) are found in the upper colon (cecum, ascending colon, and transverse colon) and, therefore, are beyond the reach of sigmoidoscopes and would be missed by flexible sigmoidoscopy.
- The National Polyp Study, a large, scientific study, has shown that colonoscopy with removal of all colon polyps reduces deaths from colon cancer.
For more information about this procedure, please see the Colonoscopy article.
Next: Virtual colonoscopy
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