The incidence of adenomas in asymptomatic average-risk persons after a negative screening colonoscopy is unknown. We previously performed a screening colonoscopy study in 496 asymptomatic average-risk persons aged 50-75 years (Am J Gastroenterol 1993;88:825). Of these, 368 were without colonic neoplasia, having either normal colonoscopy or only hyperplastic polyps. Thus far 244 of these who are approximately 5 years post initial colonoscopy have been invited to undergo repeat colonoscopy Twenty-four refused, 87 are pending or did not respond and 133 have undergone colonoscopy. Four were excluded from analysis because of incomplete repeat colonoscopy. The mean interval between exams was 66.6 mo (range 47-79 mo; 9 subjects had intervals < 60 mo). The mean age of participants was 65.9 y and there were 87 (67%) males. Among the 129 with complete colonoscopy, 39 (30%) had 57 adenomas. The largest adenoma was ≥ 10 mm in 2 persons (12 and 15 mm), 6-9 mm in 5 persons and ≤ 5 mm in 32. There were no cancers and no adenomas with severe dysplasia. Sixty-one percent of adenomas were proximal to the splenic flexure. Forty-four percent of subjects with adenomas had no adenomas distal to the splenic flexure. Among 20 persons with hyperplastic polyps at the initial study the incidence of adenomas was 30% (p=NS). Neither patient with an adenoma > 1 cm had a hyperplastic polyp at their initial colonoscopy. Among 41 persons who were regular users of NSAIDS (≥ 2 times/wk) the incidence of adenomas was 22% (p=0.14). Two vagal reactions occurred which responded to medication reversal. SUMMARY: 1) The incidence of adenomas 5 years after a negative colonoscopy in this population is similar to the initial neoplasia prevalence (26%), but the incidence of large adenomas is low (1.5%). 2) Incident adenomas are shifted toward the right colon. 3) Hyperplastic polyps at initial screening were not markers for incident adenomas. CONCLUSION: If interval colonoscopy were used to screen the average-risk population, it would appear that the interval between examinations in persons who are initially negative could be expanded beyond 5 years without significant risk.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging