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Use of water immersion instead of water exchange underlay the unfavourable outcomes in the water-assisted sigmoidoscopy (WAS) study
  1. Chih-Wei Tseng1,2,
  2. Yu-Hsi Hsieh1,2
  1. 1 Department of Medicine, Dalin Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Chiayi, Taiwan
  2. 2 School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan, Taiwan
  1. Correspondence to Dr Yu-Hsi Hsieh, Department of Medicine, Dalin Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Chiayi 62247, Taiwan; hsieh.yuhsi{at}

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We read with interest the study by Rutter and colleagues on the role of water-assisted sigmoidoscopy (WAS) in the English National Health Service bowel scope screening, showing that the proportion of patients reporting moderate or severe pain were comparable between WAS and CO2 technique (14% in WAS, 15% in CO2; p=0.47). The WAS group had statistically significantly lower adenoma detection rate (ADR) (11% vs 15%, p=0.03).1 Water-assisted colonoscopy consisted of two techniques distinguished by the timing of removal of infused water, predominantly during withdrawal (water immersion, WI) or during insertion (water exchange, WE) (figure 1). The authors stated that their method was water-assisted rather than full WE. However, as WI and WE have different impacts on insertion pain and ADR,2 we feel a need to comment on the insertion method used in the study. WE …

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  • Contributors All authors have read the Rutter et al paper in Gut. C-WT and Y-HH wrote this letter to the editor. Dr Felix Leung (VAGLAHS and UCLA, USA) provided critical review prior to submission.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.