title: Detection of proximal adenomatous polyps with screening sigmoidoscopy: a systematic review and meta-analysis of screening colonoscopy.
abstract: BACKGROUND
  The relative effectiveness of flexible sigmoidoscopy compared with colonoscopy to screen for colorectal cancer depends on the magnitude of the association between findings in the proximal and distal colon and the false-negative rate of screening sigmoidoscopy for proximal neoplasia. To address this, we performed a systematic review and meta-analysis of screening colonoscopy studies.
  
  
  METHODS
  Published studies through July 31, 2000, of asymptomatic patients undergoing screening colonoscopy were identified from the MEDLINE database. We generated pooled estimates of the odds ratio for the association between findings in the distal and proximal colon and the prevalence of isolated proximal adenomatous neoplasia.
  
  
  RESULTS
  Using the sigmoid-descending colon junction to identify the beginning of the distal colon, the pooled odds ratio for the association between distal adenomatous polyps and any proximal neoplasia was 2.40 (95% confidence interval [CI], 1.42-4.05). Diminutive distal adenomatous polyps were also associated with proximal neoplasia (odds ratio, 2.36; 95% CI, 1.30-4.29). Distal hyperplastic polyps were not associated with proximal neoplasia (odds ratio, 1.44; 95% CI, 0.79-2.62). The prevalence of isolated advanced proximal neoplasia in the 3 studies was 2%, 3%, and 5%. Using the sigmoid-descending colon junction to identify the beginning of the distal colon yields a pooled estimate of isolated proximal neoplasia of 16.3% (95% CI, 13.6%-19.1%).
  
  
  CONCLUSIONS
  Distal adenomatous polyps, including diminutive distal adenomatous polyps, are associated with an increased prevalence of synchronous proximal neoplasia. Two percent to 5% of patients undergoing screening colonoscopy may have isolated advanced proximal neoplasia. Even more patients may have isolated nonadvanced proximal neoplasia.
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, 423 Guardian Dr, Seventh Floor Blockley Hall, Philadelphia, PA 19104-6021, USA. jlewis@cceb.med.upenn.edu
authors.forename: James D
authors.initials: JD
authors.lastname: Lewis
authors.forename: Kimmie
authors.initials: K
authors.lastname: Ng
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Hung
authors.forename: Warren B
authors.initials: WB
authors.lastname: Bilker
authors.forename: Jesse A
authors.initials: JA
authors.lastname: Berlin
authors.forename: Colleen
authors.initials: C
authors.lastname: Brensinger
authors.forename: Anil K
authors.initials: AK
authors.lastname: Rustgi
mesh_terms: D018256:Adenomatous Polyps / Q000175:diagnosis* / Q000473:pathology; D003111:Colonic Polyps / Q000175:diagnosis* / Q000473:pathology; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D016015:Logistic Models; D008403:Mass Screening; D016017:Odds Ratio; D012812:Sigmoidoscopy