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Screening sigmoidoscopy may be less effective for detecting colorectal cancer in women and older people

Nearly 80 percent of colorectal cancer deaths occur in people older than 65 years. Some professional organizations recommend screening colonoscopy in people older than 50 because it permits an examination of the whole colon and has a sensitivity of 90 percent. Most guideline panels recommend screening asymptomatic people over 50 with flexible sigmoidoscopy every 5 years, annual fecal occult blood testing (examination of stool for blood), or both. However, screening for colorectal cancer with a 60-cm flexible sigmoidoscope may not be an effective screening tool for women and older individuals, according to findings from a study supported in part by the Agency for Healthcare Research and Quality (K02 HS00006). This is due to inadequate reach of the sigmoidoscope far enough past the anus to sufficiently view the whole colon, explains Kenneth E. Covinsky, M.D., M.P.H.

Dr. Covinsky and his colleagues measured the maximum depth of insertion of the sigmoidoscope among 15,406 asymptomatic people who underwent the screening procedure between April 1997 and October 2001 at 71 sites in 27 States. The researchers defined 50 cm or more from the anus as adequate and less than 50 cm as inadequate. Overall, 18 percent of patients had an inadequate examination. In men, the percentage of inadequate exams increased progressively with age, from 10 percent in those aged 50 to 59 years to 22 percent in those aged 80 years or older.

Inadequate exams were more common in women at all ages, ranging from 19 percent in those aged 50 to 59 years to 32 percent in those aged 80 years or older. The proportion of polyps and cancers located beyond 50 cm from the anus is increased in these groups. Women are more likely to experience pain during flexible sigmoidoscopy than men, and they have longer colons in a smaller abdominal cavity, resulting in more twists and turns that make endoscope passage difficult. Older adults tend to have poor bowel preparation before the procedure, more coexisting problems such as prior abdominal surgeries, and more severe diverticular disease.

See "Association of older age and female sex with inadequate reach of screening flexible sigmoidoscopy," by Louise C. Walter, M.D., Pat deGarmo, A.N.P., M.U.P., and Dr. Covinsky, in the American Journal of Medicine 116, pp. 174-178, 2004.

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