The impact of colon preparation timing on colonoscopic detection of colorectal neoplasms--a prospective endoscopist-blinded randomized trial

Am J Gastroenterol. 2006 Dec;101(12):2719-25. doi: 10.1111/j.1572-0241.2006.00868.x. Epub 2006 Oct 6.


Objectives: Timing of colon preparation might influence the cleansing condition of the colon and therefore affect the quality and diagnostic yield of colonoscopy. This study compared two different timings of colon preparation to assess the efficacy of colon cleansing and diagnostic yield of colorectal neoplasms during colonoscopy.

Methods: One hundred twenty-one eligible subjects who had colorectal neoplasms detected at a screening colonoscopy were randomly assigned to receive colon preparation with polyethylene glycol electrolyte lavage solution (PEG-ELS) either on the day of (on the day group) or the night before (previous night group) a second colonoscopy. The condition of colon preparation and the diagnostic yield of colorectal neoplasms were recorded and compared between the two groups for the initial and second colonoscopies.

Results: Fifty-nine subjects received colon preparation on the night before and 60 subjects received colon preparation the day of a second colonoscopy. Colon preparation for the second colonoscopy was better in the on-the-day group than in the previous night group (P= 0.003). Colon preparation for the second colonoscopy was better for each group in comparison with the initial colonoscopy (P < 0.0001). An interobserver variability analysis using 20 randomly selected colonoscopies from the two groups revealed good correlation among four colonoscopists. More lesions were detected in group A during the second colonoscopy (P= 0.028).

Conclusion: Colon preparation on the day of colonoscopy has a better cleansing quality and higher diagnostic yield. Subjects who had lesions detected during the initial screening colonoscopy had better colon cleansing for the second colonoscopy regardless of the timing of preparation.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Colonoscopy*
  • Colorectal Neoplasms / pathology*
  • Drug Administration Schedule
  • Female
  • Humans
  • Male
  • Middle Aged
  • Polyethylene Glycols / administration & dosage*
  • Preoperative Care / methods*
  • Prospective Studies
  • Single-Blind Method
  • Surface-Active Agents / administration & dosage*
  • Therapeutic Irrigation / methods


  • Surface-Active Agents
  • Polyethylene Glycols