Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy

Background: The prevalence of missed polyps in patients with inadequate bowel preparation on screening colonoscopy is unknown. Objective: To determine the prevalence of missed adenomas in average-risk patients presenting for screening colonoscopy who are found to have inadequate bowel preparation. Design: Retrospective chart review. Endoscopy and pathology reports were examined to determine the characteristics of polyps. Data from repeat colonoscopies were collected through 2010. Setting: Outpatient endoscopy center at an academic medical center. Patients: This study involved patients who underwent outpatient average-risk screening colonoscopy between 2004 and 2009 documented to have inadequate bowel preparation and who had colonoscopy to the cecum. Main Outcome Measurements: Initial adenoma detection rate and adenoma detection rate on follow-up examination. Results: Inadequate bowel preparation was reported on 373 patients, with an initial adenoma detection rate of 25.7%. Of 133 patients who underwent repeat colonoscopy, 33.8% had at least 1 adenoma detected, and 18.0% had high-risk states detected (>= 3 adenomas, 1 adenoma >= 1 cm, or any adenoma with villous features or high-grade dysplasia). Per-adenoma miss rate was 47.9%. Among patients with at least 1 adenoma on repeat colonoscopy, 31.1% had no polyps on initial colonoscopy; mean time between colonoscopies was 340 days. Among patients with high-risk states, 25.0% had no polyps seen on initial colonoscopy; mean time between colonoscopies was 271 days. Limitations: Retrospective design. Conclusion: Adenomas and high-risk lesions were frequently detected on repeat colonoscopy in patients with inadequate bowel preparation on initial screening colonoscopy, suggesting that these lesions were likely missed on initial colonoscopy. (Gastrointest Endosc 2012;75:1197-203.)