title: Preoperative endoscopy localization error rate in patients with colorectal cancer.
abstract: BACKGROUND
  Preoperative repeat endoscopy in colorectal cancer (CRC) patients is considered by many to be an integral component of surgical planning. Little is known, however, about the utility of re-endoscopy.
  
  
  METHODS
  A retrospective review of 342 consecutive patients undergoing elective surgical resection for CRC from January 2008 to December 2011 was performed. Patients were included if the initial endoscopist was different than the operating surgeon. A localization error was recorded if the final tumor location identified during surgery was in a different anatomical segment than that identified by endoscopy. The Chi-squared test was used to compare categorical variables. An error rate with a 95% confidence interval was obtained using the exact binomial distribution.
  
  
  RESULTS
  298 patients were identified, 118 (39.6%) of whom also underwent a preoperative re-endoscopy by the operating surgeon or partner. Nineteen patients had incorrect tumor localization at initial endoscopy, equivalent to a 6.4% error rate (95% CI 3.88-9.78). In comparison, there were two localization errors on re-endoscopy, 1.69% (95% CI 0.21-6.00). Re-endoscopy was found to be protective against localization errors (P < 0.05), correcting 10 of the 12 errors made at the initial endoscopy. The sensitivity of re-endoscopy as a diagnostic tool to detect errors was 83% with a corresponding specificity of 100%. The overall accuracy of re-endoscopy in preventing endoscopic localization errors was 92% (95% CI 81-100).
  
  
  CONCLUSIONS
  There is a small but important localization error rate in preoperative endoscopic evaluation of colorectal tumors. Re-endoscopy appears to be safe and may potentially identify and correct these errors and help with preoperative planning at the expense of delaying surgery. Further research is necessary to find ways to improve localization and identify which patients would benefit from re-endoscopy.
authors.affiliation: Division of General Surgery, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Room 8MP-320, Toronto, ON, M5T 2S8, Canada.
authors.forename: Fady
authors.initials: F
authors.lastname: Saleh
authors.forename: Thamer Al
authors.initials: TA
authors.lastname: Abbasi
authors.forename: Michelle
authors.initials: M
authors.lastname: Cleghorn
authors.forename: M Carolina
authors.initials: MC
authors.lastname: Jimenez
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Jackson
authors.forename: Allan
authors.initials: A
authors.lastname: Okrainec
authors.forename: Fayez A
authors.initials: FA
authors.lastname: Quereshy
mesh_terms: D019985:Benchmarking; D016009:Chi-Square Distribution; D015331:Cohort Studies; D003113:Colonoscopy / Q000592:standards*; D015179:Colorectal Neoplasms / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009864:Ontario; D017063:Outcome Assessment, Health Care; D011300:Preoperative Care / Q000592:standards; D012189:Retrospective Studies; D012680:Sensitivity and Specificity