The role of sigmoidoscopy for asymptomatic patients. Results of three annual screening sigmoidoscopies, polypectomy, and subsequent surveillance colonoscopy in a primary-care setting.

A total of 329 asymptomatic patients (aged 50 or older) underwent flexible sigmoidoscopy to screen for colonic neoplasia. Of these, 258 underwent a second examination after 1 year and 143 underwent a third examination after another year. Of 60 patients in whom polyps were found on one of the three examinations, 58 underwent colonoscopy and polypectomy; 77 adenomatous polyps were present in 39 of these patients. The incidence of adenomatous polyps was 7.9% for the first examination, 3.9% for the second, and 2.1% for the third. Of patients with an index polyp found by sigmoidoscopy, 57.5% had synchronous polyps discovered by colonoscopy. Thirty-six of 77 polyps in 24 patients showed dysplasia; 9 were less than 0.5 cm, 14 were 0.5 cm to 0.9 cm, and 13 were 1 cm or larger. Forty-four surveillance colonoscopies (done after initial colonoscopy and polypectomy) have been performed in 28 patients. Eighteen examinations resulted in finding 30 adenomatous polyps, of which 10 showed dysplasia. This study 1) is the first report of flexible sigmoidoscopy data to support the American Cancer Society recommendation of two serial screening sigmoidoscopies a year apart, 2) reinforces the concept that an index polyp indicates a need for a complete colonoscopy, 3) reinforces the need for ongoing surveillance by colonoscopy after detection of adenomas, and 4) adds to reports of dysplasia in diminutive polyps.