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African American Health

African Amer & Cancer in the Proximal Colon

10/24/2006

Question:

In the NetWellness article by Julia Gore Thornton, it states:

Emerging research also suggests that African Americans are more likely than Whites to have precancerous polyps and colon cancer in the proximal colon, which could potentially be missed if screening was done by flexible sigmoidoscopy alone."

Where is the proximal colon and why is it not able to be screened using flexible sigmoidoscopy? Has any research showed why African Americans are more likely to develop polyps and cancer in this location of the body?

Answer:

The scopes used to perform flexible sigmoidoscopy are shorter than the scopes used to do colonoscopies. Since the colonoscopy scopes are longer, the entire colon is visualized and since the flexible sigmoidoscopy scopes are shorter, the entire colon usually can't be evaluated.

If you look at a picture of the colon, it is usually divided into different parts: ascending colon, transverse colon, descending colon, sigmoid colon and rectum. The proximal colon usually refers to the ascending colon and transverse colon. This is also the area that usually cannot be seen by flexible sigmoidoscopy.

We don't know why African Americans are more likely to develop polyps and cancer in the proximal colon. Researchers speculate that diet may play a role but there's no definite known reason as of yet.

For more information:

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Response by:

Julia Gore Thornton, MD Julia Gore Thornton, MD
Assistant Professor of Medicine
School of Medicine
Case Western Reserve University