Condition category
Digestive System
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
Bowel cancer is the second most common cause of cancer death in the UK. Around 1 in 14 men and 1 in 19 women will develop bowel cancer. To reduce this risk, the NHS Bowel Screening Programme has started inviting all 55 year olds for a sigmoidoscopy. This involves examining the lower bowel with a thin flexible tube with a camera on it, via the back passage. Research has shown that this test reduces bowel cancer death by 41%. During the test, the bowel is inflated with carbon dioxide, to allow passage of the camera. The problem is that bowel distention can cause pain. National surveys show that over 1 in 3 patients report moderate or severe pain. The aim of this study is to assess whether using water to minimise bowel distension, instead of gas, will make the procedure more comfortable. Early studies suggest this may be effective, but this needs to be confirmed in UK practice. It is hoped that by reducing pain, people will have a better experience, which may increase public uptake of screening. Currently only 43.7% of people participate –more cancers can be prevented if participation increases.

Who can participate?
Healthy volunteers referred for screening flexible sigmoidoscopy via the NHS Bowel Scope Screening Programme

What does the study involve?
Participants are randomly allocated to either have the current standard sigmoidoscopy using carbon dioxide, or to have sigmoidoscopy using water. Participants are then asked how comfortable they found the test. The study also measures which technique finds more polyps (small growths that may have cancerous potential).

What are the possible benefits and risks of participating?
The endoscopists performing the procedure may be able to deliver a more comfortable procedure for patients and may also be able to find more polyps. The study may not benefit the participants now, but the results may help others who have sigmoidoscopy in the future. There have been no safety issues reported with water-assisted sigmoidoscopy in any study so far. Discomfort is a possibility in either type of sigmoidoscopy procedure (normal CO2 sigmoidoscopy and water-assisted sigmoidoscopy). As part of the study side effects (such as discomfort and incontinence during or after the procedure) as well as overall experience during the flexible sigmoidoscopy are measured.

Where is the study run from?
1. North Tees and Hartlepool NHS Foundation Trust (UK)
2. St Mark's Hospital, London (UK)
3. South Tyneside NHS Foundation Trust (UK)
4. Queen Elizabeth Hospital Gateshead (UK)
5. County Durham and Darlington NHS Foundation Trust (UK)

When is the study starting and how long is it expected to run for?
June 2017 to November 2019

Who is funding the study?
National Institute for Health Research (NIHR) (UK)

Who is the main contact?
Mrs Jill Deane

Trial website

Contact information



Primary contact

Mrs Jill Deane


Contact details

Research Office
2nd Floor
South Wing
University Hospital of North Tees
Stockton on Tees
TS19 8PE
United Kingdom
+44 (0)1642 624582

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

The WASH study: water assisted sigmoidoscopy in NHS Bowel Scope Screening Programme: a randomised multicentre study



Study hypothesis

1. Water-assisted sigmoidoscopy (WAS) will lead to decreased procedural pain, when compared with standard CO2-assisted (CO2) insertion, resulting in better patient experience during screening
2. WAS improves other key screening performance indicators such as the adenoma (cancer precursor) detection rate

Ethics approval

NRES Committee North East, 10/11/2017, ref: 17/NE/0309

Study design

Randomised; Interventional; Design type: Treatment, Other

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Specialty: Gastroenterology, Primary sub-specialty: Endoscopy and imaging; UKCRC code/ Disease: Oral and Gastrointestinal/ Other diseases of the digestive system


Patients will be randomised using a secure, web-based platform that can be accessed 24 hours a day, which was developed and is maintained by NWORTH. The randomisation uses dynamic allocation to ensure a consistent balance to the allocation ratio of 1:1 and within any stratification variable.

Treatment: water-assisted flexible sigmoidoscopy (FSIG) utilising the WAS technique
Control: standard CO2 assisted flexible sigmoidoscopy

The trialists will then ask patients how comfortable they found the test and measure which technique finds more adenomas. Follow-up is for 14 days following procedure (sigmoidoscopy).

Intervention type



Drug names

Primary outcome measure

Pain is measured using a standard Likert scale (4-point) (“None/ Mild / Moderate / Severe”) post-procedure/pre-discharge and 24 hours afterwards via patient questionnaire

Secondary outcome measures

The key secondary outcome will be the adenoma detection rate (ADR), the key performance indicator for the accuracy of sigmoidoscopy in detecting pre-malignant polyps (adenomas). This is measured at 14 days following review of all histology reports of patient who have polyps removed

Other secondary measures include:
1. Procedural pain as rated by patients on a Visual Analogue Scale (VAS) immediately after procedure [post-procedure, pre-discharge]
2. Other aspects of patients’ experience, by a post-discharge questionnaire assessing embarrassment, willingness to repeat the procedure, expected versus experienced pain, overall satisfaction and symptoms post-procedure.
3. The sigmoidoscopy insertion times (SITs)
4. The sigmoidoscopy withdrawal times (SWTs) in negative procedures (i.e. without polyps)
5. The maximum extent of insertion (segment, i.e. rectum, distal sigmoid, proximal sigmoid, distal descending, proximal descending, splenic flexure, distal transverse; as judged by the endoscopist) – this will be the primary means to estimate extent of insertion
6. The final length of scope inserted just prior to withdrawal (scope length in cm) – this will be used as a surrogate for how straight/looped the scope is (stratifying by segment extent)
7. The mean number of adenomas per procedure (MAP)
8. The percentage of procedures where Entonox was used on demand (i.e. as an adjunct in case of procedural pain per patient’s wish). This will not be applicable in procedures where participants prefer to start their procedure with Entonox use
9. The quality of mucosal views on withdrawal using the validated Boston Bowel Preparation Scale
10. The percentage of procedures where a second enema was needed (due to poor mucosal views)
11. The percentage of procedures where hand pressure was required (ancillary manoeuvre to aid insertion)
12. The percentage of procedures where patient position shifts were required (ancillary manoeuvre to aid insertion)
13. The conversion rate from WAS to CO2, or CO2 to WAS technique
14. The volume of water and CO2 used in WAS and CO2 arms
15. The number and type of endoscope loops identified with magnetic scope guide (where scope guide used)
16. The endoscopist learning curve of WAS technique during the training period (prior to commencing the trial) by capturing endoscopists’ reported confidence in performing the procedure, their attitude towards the technique (negative, neutral, positive) before and after completion of training period, as well as procedure times and extent of insertion as the study progresses

These outcomes will be analysed on an intention to treat basis. Following this; as per protocol analysis will be considered as appropriate to assess the sensitivity of these results.
Exploratory subgroups analyses will be considered for relevant cohorts with previous hysterectomy, irritable bowel syndrome and diverticulosis, as well as for depth of scope insertion (segment and length of scope), scope diameter (adult vs. paediatric) and model (e.g. Olympus 240/260/290) and individual endoscopists all considered.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Referral for screening flexible sigmoidoscopy via the NHS Bowel Scope Screening Programme
2. Ability to give informed consent

Participant type

Healthy volunteer

Age group




Target number of participants

Planned Sample Size: 1100; UK Sample Size: 1100

Participant exclusion criteria

1. Absolute contraindications to sigmoidoscopy
2. Patients lacking capacity to give informed consent
3. Previous left colonic/rectal resection
4. Ongoing antithrombotic treatment (apart from aspirin, which is permitted)

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

North Tees and Hartlepool NHS Foundation Trust
TS19 8PE

Trial participating centre

St Mark's Hospital

Trial participating centre

South Tyneside NHS Foundation Trust
NE34 0PL

Trial participating centre

Queen Elizabeth Hospital

Trial participating centre

County Durham and Darlington NHS Foundation Trust

Sponsor information


North Tees & Hartlepool NHS Foundation Trust

Sponsor details

University Hospital of Hartlepool
Holdforth Road
TS24 9AH
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type


Funder name

NIHR Central Commissioning Facility (CCF); Grant Codes: PB-PG-1215-20035

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Results of the study will be published in an international journal and will be communicated to the Bowel Cancer Screening Programme and to patients and doctors internationally.

IPD sharing statement
Once the trial is complete and all data collection, data cleaning, data analysis and reports are complete the Chief Investigator will be issued with a trial data pack by NOWRTH (all data will be anonymised). Chief Investigator is Professor Matt Rutter (

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes