Repeat colonoscopy has a low yield even in symptomatic patients.
BACKGROUND: In many regions, the demand for colonoscopy exceeds its availability. Patients undergoing repeat examinations comprise a significant proportion of those on waiting lists. OBJECTIVE: To assess the yield of repeat colonoscopy in varied clinical settings. DESIGN: Cohort study. SETTING: Endoscopic database of an Australian tertiary referral hospital. PATIENTS: Adults who had >/=2 colonoscopies between 1992 and 2004. Patients were excluded if the repeat procedure was for completion or for high-risk surveillance. MAIN OUTCOME MEASUREMENTS: Yield for neoplasia by indication, interval to repeat examination, and appropriateness for surveillance (determined by National Australian guidelines). RESULTS: A total of 4974 colonoscopies in 2075 patients were studied. The mean age was 63.1 years (range, 19.2-92.4 years). The mean number of examinations was 2.4 (range, 2-8), with a mean interval between examinations of 2.9 years. Colorectal cancer (CRC) was significantly more prevalent at initial colonoscopy compared with subsequent colonoscopies (7.9% vs 0.6%; prevalence ratio 14.2, 95% confidence interval [CI] 8.5-23.7, P < .001), as were advanced adenomas (15.3% vs 4.8%; prevalence ratio 3.2, 95% CI 2.6-3.9, P < .001). No CRCs were detected in symptomatic patients undergoing polyp surveillance examinations performed before the recommended interval. LIMITATIONS: Retrospective design. CONCLUSIONS: Yield of repeat colonoscopy is significantly lower than for initial colonoscopy, irrespective of indication. In symptomatic patients within a polyp surveillance program, the yield is negligible when a colonoscopy is performed before the recommended surveillance interval. The need for a repeat colonoscopy should be carefully considered, and patients who have never had a colonoscopy must take priority on waiting lists over those awaiting repeat examinations.