Significance of a normal surveillance colonoscopy in patients with a history of adenomatous polyps

PURPOSE: The aim of this study was to determine the appropriate surveillanc e for patients with a history of adenomatous polyps whose last colonoscopic examination was normal. METHODS: This was a retrospective review of a data base of 7,677 colonoscopies (1990 to 1996). In patients under colonoscopic surveillance, we reviewed cases of patients who had received three colonosc opies tan index (initial) colonoscopy positive for adenomas and 2 follow-up colonoscopies (interim and final)). The risk of adenomas and cancers at fi nal follow-up colonoscopy was compared between patients having a normal int erim colonoscopy and those with a positive interim colonoscopy. The risk at final colonoscopy was also stratified by time interval and the size and nu mber of adenomas at the initial index colonoscopy. RESULTS: Two hundred fou r patients undergoing surveillance for adenomas met inclusion criteria. At index colonoscopy the median polyp size was 1 cm and median frequency was t hree polyps. At all follow-up colonoscopies, we detected 493 adenomas and o ne cancer (median follow-up, 55 months). At 36 months patients with a norma l interim colonoscopy (n = 91) had significantly fewer polyps than patients with a positive interim colonoscopy (n = 113; 15 vs. 40 percent; P = 0.000 1). By 10 months, adenomas were detected in more than 40 percent of patient s in both groups. The risk after a normal interim colonoscopy was not affec ted by time interval or number or size of polyps. Adenomas found subsequent to a normal interim colonoscopy were dispersed throughout the colon in 28 patients and isolated to the rectosigmoid in 6 patients. CONCLUSIONS: in pa tients with a history of adenomas, a normal follow-up colonoscopy is associ ated with a statistically but not clinically significant reduction in the r isk of subsequent colonic neoplasms. These patients require follow-up surve illance colonoscopy at a four-year to five-year interval.