A randomized, controlled trial comparing real-time insertion pain during colonoscopy confirmed water exchange to be superior to water immersion in enhancing patient comfort

Gastrointest Endosc. 2015 Mar;81(3):557-66. doi: 10.1016/j.gie.2014.07.029. Epub 2014 Sep 26.


Background: A recent American Society for Gastrointestinal Endoscopy Technology Status Evaluation Report recommended comparative studies of water-aided colonoscopy methods to refine the optimal insertion technique.

Objective: Air insufflation (AI), water immersion (WI), and water exchange (WE) were compared head-to-head to test the hypothesis that WE produces the least insertion pain.

Design: Patient-blinded, prospective, randomized, controlled trials.

Setting: Two community hospitals in Italy.

Patients: First-time diagnostic or screening colonoscopy in unsedated patients with the option of on-demand sedation.

Intervention: Colonoscopy with AI, WI, or WE.

Main outcome measurements: Real-time maximum insertion pain (0 = none, 10 = worst). To avoid interventional bias, the timing of recording was at the discretion of the nurse assistant. Adjunct measures were implemented to ensure patient perception of minimal discomfort. Recalled pain and patients' guess of insertion methods were recorded after colonoscopy.

Results: Results were merged for 576 randomized patients. Correct patient guesses lower than 33% confirmed adequate blinding. Significant correlation (Pearson coefficient 0.6, P < .0005) between real-time and recalled pain provided internal validation of the former as the primary outcome. Real-time pain (95% confidence interval [CI]: AI, 4.1 [3.7-4.5]; WI, 3.5 [3.0-3.9]; and WE, 2.5 [2.2-2.9] [P < .0005] was the lowest in the WE group. The proportions of patients completing unsedated colonoscopy based on the assigned methods were significantly different (WE, 74.7% vs WI, 62.4%; P = .009; vs AI, 65.3%; P = .04). WE required the least implementation of adjunct maneuvers.

Limitations: Unblinded colonoscopists.

Conclusion: The current findings with an internally validated primary outcome in adequately blinded patients support the hypothesis that WE is superior to WI in attenuating real-time insertion pain and enhancing completion of unsedated colonoscopy.

Trial registration: ClinicalTrials.gov NCT01780818 NCT01781650.

Publication types

  • Comparative Study
  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Colonoscopy / adverse effects
  • Colonoscopy / methods*
  • Female
  • Humans
  • Insufflation
  • Logistic Models
  • Male
  • Middle Aged
  • Pain / diagnosis
  • Pain / etiology
  • Pain / prevention & control*
  • Pain Measurement
  • Patient Satisfaction
  • Prospective Studies
  • Single-Blind Method
  • Water*
  • Young Adult


  • Water

Associated data

  • ClinicalTrials.gov/NCT01780818
  • ClinicalTrials.gov/NCT01781650