title: Natural history of diminutive colorectal polyps: long-term prospective observation by colonoscopy.
abstract: OBJECTIVE
  Endoscopic removal of colorectal adenomatous polyps effectively prevents cancer. However, the treatment strategy for diminutive polyps (diameter ≤ 5 mm) remains controversial. Understanding the natural history of diminutive polyps is a prerequisite to their effective management. We prospectively examined the natural history of diminutive polyps by long-term surveillance colonoscopy.
  
  
  METHODS
  A total of 207 polyps detected in 112 patients from December 1991 through March 2002 were studied. To avoid potential effects on size and morphological characteristics, all polyps were selected randomly and were followed without biopsy. Polyp size was estimated by comparing the lesion with the diameter of a biopsy forceps.
  
  
  RESULTS
  Mean follow up was 7.8 years (SD, 4.8; range, 1.0-18.6; median, 7.5; interquartile range 3.4-11.2). Twenty-four polyps were resected endoscopically, and the histopathological diagnosis was mucosal high-grade neoplasia (Category 4) for one polyp, and mucosal low-grade neoplasia (Category 3) for 23 polyps. Mean linear size of the polyps was 3.2 mm (SD, 1.0; range, 1.3-5.0) at initial colonoscopy and 3.8 mm (SD 1.6; range 1.3-10.0) at final colonoscopy (P<0.01). Left-sided polyps showed a higher growth rate than right-sided polyps, and a type IIIL2 pit pattern was associated with a lower growth rate than a type IIIL1 pattern.
  
  
  CONCLUSIONS
  We clarified the natural history of diminutive polyps by long-term follow-up colonoscopy. The benign course of diminutive polyps should be considered in the design of treatment strategies.
authors.affiliation: Department of Endoscopy, Niigata University Hospital, Niigata, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Mizuno
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Manabu
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Aoyagi
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003111:Colonic Polyps / Q000473:pathology* / Q000503:physiopathology; D003113:Colonoscopy / Q000379:methods*; D015179:Colorectal Neoplasms / Q000473:pathology* / Q000503:physiopathology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007150:Immunohistochemistry; D007564:Japan; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D011446:Prospective Studies; D013997:Time Factors
keywords: adenoma; colonoscopy; colorectal adenoma; diminutive polyp; natural history