The effect of aspirin and eicosapentaenoic acid on urinary biomarkers of prostaglandin E2 synthesis and platelet activation in participants of the seAFOod polyp prevention trial.

Urinary prostaglandin (PG) E metabolite (PGE-M) and 11-dehydro (d)-thromboxane (TX) B2 are biomarkers of cyclooxygenase-dependent prostanoid synthesis. We investigated (1) the effect of aspirin 300 mg daily and eicosapentaenoic acid (EPA) 2000 mg daily, alone and in combination, on urinary biomarker levels and, (2) whether urinary biomarker levels predicted colorectal polyp risk, during participation in the seAFOod polyp prevention trial. Urinary PGE-M and 11-d-TXB2 were measured by liquid chromatography-tandem mass spectrometry. The relationship between urinary biomarker levels and colorectal polyp outcomes was investigated using negative binomial (polyp number) and logistic (% with one or more polyps) regression models. Despite wide temporal variability in PGE-M and 11-d-TXB2 levels within individuals, both aspirin and, to a lesser extent, EPA decreased levels of both biomarkers (74% [P ≤ .001] and 8% [P ≤ .05] reduction in median 11-d-TXB2 values, respectively). In the placebo group, a high (quartile [Q] 2-4) baseline 11-d-TXB2 level predicted increased polyp number (incidence rate ratio [IRR] [95% CI] 2.26 [1.11,4.58]) and risk (odds ratio [95% CI] 3.56 [1.09,11.63]). A low (Q1) on-treatment 11-d-TXB2 level predicted reduced colorectal polyp number compared to placebo (IRR 0.34 [0.12,0.93] for combination aspirin and EPA treatment) compared to high on-treatment 11-d-TXB2 values (0.61 [0.34,1.11]). Aspirin and EPA both inhibit PGE-M and 11-d-TXB2 synthesis in keeping with shared in vivo cyclooxygenase inhibition. Colorectal polyp risk and treatment response prediction by 11-d-TXB2 is consistent with a role for platelet activation during early colorectal carcinogenesis. The use of urinary 11-d-TXB2 measurement for a precision approach to colorectal cancer risk prediction and chemoprevention requires prospective evaluation.

The performance of FIT-based and other risk prediction models for colorectal neoplasia in symptomatic patients: a systematic review.

Background: Colorectal cancer (CRC) incidence and mortality are increasing internationally. Endoscopy services are under significant pressure with many overwhelmed. Faecal immunochemical testing (FIT) has been advocated to identify a high-risk population of symptomatic patients requiring definitive investigation by colonoscopy. Combining FIT with other factors in a risk prediction model could further improve performance in identifying those requiring investigation most urgently. We systematically reviewed performance of models predicting risk of CRC and/or advanced colorectal polyps (ACP) in symptomatic patients, with a particular focus on those models including FIT. Methods: The review protocol was published on PROSPERO (CRD42022314710). Searches were conducted from database inception to April 2023 in MEDLINE, EMBASE, Cochrane libraries, SCOPUS and CINAHL. Risk of bias of each study was assessed using The Prediction study Risk Of Bias Assessment Tool. A narrative synthesis based on the guidelines for Synthesis Without Meta-Analysis was performed due to study heterogeneity. Findings: We included 62 studies; 23 included FIT (n = 22) or guaiac Faecal Occult Blood Testing (n = 1) combined with one or more other variables. Twenty-one studies were conducted solely in primary care. Generally, prediction models including FIT consistently had good discriminatory ability for CRC/ACP (i.e. AUC >0.8) and performed better than models without FIT although some models without FIT also performed well. However, many studies did not present calibration and internal and external validation were limited. Two studies were rated as low risk of bias; neither model included FIT. Interpretation: Risk prediction models, including and not including FIT, show promise for identifying those most at risk of colorectal neoplasia. Substantial limitations in evidence remain, including heterogeneity, high risk of bias, and lack of external validation. Further evaluation in studies adhering to gold standard methodology, in appropriate populations, is required before widespread adoption in clinical practice. Funding: National Institute for Health and Care Research (NIHR) [Health Technology Assessment Programme (HTA) Programme (Project number 133852).

Polymorphisms in Cyclooxygenase, Lipoxygenase, and TP53 Genes Predict Colorectal Polyp Risk Reduction by Aspirin in the seAFOod Polyp Prevention Trial.

Aspirin and eicosapentaenoic acid (EPA) reduce colorectal adenomatous polyp risk and affect synthesis of oxylipins including prostaglandin E2. We investigated whether 35 SNPs in oxylipin metabolism genes such as cyclooxygenase (PTGS) and lipoxygenase (ALOX), as well as 7 SNPs already associated with colorectal cancer risk reduction by aspirin (e.g., TP53; rs104522), modified the effects of aspirin and EPA on colorectal polyp recurrence in the randomized 2 × 2 factorial seAFOod trial. Treatment effects were reported as the incidence rate ratio (IRR) and 95% confidence interval (CI) by stratifying negative binomial and Poisson regression analyses of colorectal polyp risk on SNP genotype. Statistical significance was reported with adjustment for the false discovery rate as the P and q value. 542 (of 707) trial participants had both genotype and colonoscopy outcome data. Reduction in colorectal polyp risk in aspirin users compared with nonaspirin users was restricted to rs4837960 (PTGS1) common homozygotes [IRR, 0.69; 95% confidence interval (CI), 0.53-0.90); q = 0.06], rs2745557 (PTGS2) compound heterozygote-rare homozygotes [IRR, 0.60 (0.41-0.88); q = 0.06], rs7090328 (ALOX5) rare homozygotes [IRR 0.27 (0.11-0.64); q = 0.05], rs2073438 (ALOX12) common homozygotes [IRR, 0.57 (0.41-0.80); q = 0.05], and rs104522 (TP53) rare homozygotes [IRR, 0.37 (0.17-0.79); q = 0.06]. No modification of colorectal polyp risk in EPA users was observed. In conclusion, genetic variants relevant to the proposed mechanism of action on oxylipins are associated with differential colorectal polyp risk reduction by aspirin in individuals who develop multiple colorectal polyps. SNP genotypes should be considered during development of personalized, predictive models of colorectal cancer chemoprevention by aspirin. PREVENTION RELEVANCE: Single-nucleotide polymorphisms in genes controlling lipid mediator signaling may modify the colorectal polyp prevention activity of aspirin. Further investigation is required to determine whether testing for genetic variants can be used to target cancer chemoprevention by aspirin to those who will benefit most.

Quality in colonoscopy: time to ensure national standards are implemented?

Background: High-quality colonoscopy is crucial to ensure complete mucosal visualisation and to maximise detection of pathology. Previous audits showing variable quality have prompted national and international colonoscopy improvement programmes, including the development of quality assurance standards and key performance indicators (KPIs). The most widely used marker of mucosal visualisation is the adenoma detection rate (ADR), however, histological confirmation is required to calculate this. We explored the relationship between core colonoscopy KPIs. Methods: Data were collected from colonoscopists in eight hospitals in North East England over a 6-month period, as part of a quality improvement study. Procedural information was collected including number of colonoscopies, caecal intubation rate (CIR), ADR and polyp detection rate (PDR). Associations between KPIs and colonoscopy performance were analysed. Results: 9265 colonoscopies performed by 118 endoscopists were included. Mean ADR and PDR per endoscopist were 16.6% (range 0-36.3, SD 7.4) and 27.2% (range 0-57.5, SD 9.3), respectively. Mean number of colonoscopies conducted in 6 months was 78.5 (range 4-334, SD 61). Mean CIR was 91.2% (range 55.5-100, SD 6.6). Total number of colonoscopies and ADR>15% were significantly associated (p=0.04). Undertaking fewer colonoscopies and using hyoscine butylbromide less frequently was significantly associated with ADR<15%. CIR, endoscopist grade, % male patients, mean patient age and CIR were not significantly related to ADR<15%. In adjusted analyses, factors which affected ADR were PDR and mean patient age. Conclusion: Colonoscopists who perform fewer than the nationally stipulated minimum of 100 procedures per year had significantly lower ADRs. This study demonstrates that PDR can be used as a marker of ADR; providing age is also considered.

Colorectal polyp outcomes after participation in the seAFOod polyp prevention trial: Evidence of rebound elevated colorectal polyp risk after short-term aspirin use.

BACKGROUND: The seAFOod polyp prevention trial was a randomised, placebo-controlled, 2 × 2 factorial trial of aspirin 300 mg and eicosapentaenoic acid (EPA) 2000 mg daily in individuals who had a screening colonoscopy in the English Bowel Cancer Screening Programme (BCSP). Aspirin treatment was associated with a 20% reduction in colorectal polyp number at BCSP surveillance colonoscopy 12 months later. It is unclear what happens to colorectal polyp risk after short-term aspirin use. AIM: To investigate colorectal polyp risk according to the original trial treatment allocation, up to 6 years after trial participation. METHODS: All seAFOod trial participants were scheduled for further BCSP surveillance and provided informed consent for the collection of colonoscopy outcomes. We linked BCSP colonoscopy data to trial outcomes data. RESULTS: In total, 507 individuals underwent one or more colonoscopies after trial participation. Individuals grouped by treatment allocation were well matched for clinical characteristics, follow-up duration and number of surveillance colonoscopies. The polyp detection rate (PDR; the number of individuals who had ≥1 colorectal polyp detected) after randomization to placebo aspirin was 71.1%. The PDR was 80.1% for individuals who had received aspirin (odds ratio [OR] 1.13 [95% confidence interval 1.02, 1.24]; p = 0.02). There was no difference in colorectal polyp outcomes between individuals who had been allocated to EPA compared with its placebo (OR for PDR 1.00 [0.91, 1.10]; p = 0.92). CONCLUSION: Individuals who received aspirin in the seAFOod trial demonstrated increased colorectal polyp risk during post-trial surveillance. Rebound elevated neoplastic risk after short-term aspirin use has important implications for aspirin cessation driven by age-related bleeding risk. ISRCTN05926847.

High quality colonoscopy: using textbook process as a composite quality measure.

BACKGROUND : High quality colonoscopy is fundamental to good patient outcomes. "Textbook outcome" has proven to be a feasible multidimensional measure for quality assurance between surgical centers. In this study, we sought to establish the "textbook process" (TP) as a new composite measure for the optimal colonoscopy process and assessed how frequently TP was attained in clinical practice and the variation in TP between endoscopists. METHODS : To reach consensus on the definition of TP, international expert endoscopists completed a modified Delphi consensus process. The achievement of TP was then applied to clinical practice. Prospectively collected data in two endoscopy services were retrospectively evaluated. Data on colonoscopies performed for symptoms or surveillance between 1 January 2018 and 1 August 2021 were analyzed. RESULTS : The Delphi consensus process was completed by 20 of 27 invited experts (74.1 %). TP was defined as a colonoscopy fulfilling the following items: explicit colonoscopy indication; successful cecal intubation; adequate bowel preparation; adequate withdrawal time; acceptable patient comfort score; provision of post-polypectomy surveillance recommendations in line with guidelines; and the absence of the use of reversal agents, early adverse events, readmission, and mortality. In the two endoscopy services studied, TP was achieved in 5962/8227 colonoscopies (72.5 %). Of 48 endoscopists performing colonoscopy, attainment of TP varied significantly, ranging per endoscopist from 41.0 % to 89.1 %. CONCLUSION : This study proposes a new composite measure for colonoscopy, namely "textbook process." TP gives a comprehensive summary of performance and demonstrates significant variation between endoscopists, illustrating the potential benefit of TP as a measure in future quality assessment programs.

The effect of the endoscopic device Endocuff™/Endocuff vision™ on quality standards in colonoscopy: A systematic review and meta-analysis of randomized trials.

AIM: The adenoma detection rate (ADR) is an important quality measure, with a high ADR reflecting high-quality colonoscopy. This systematic review and meta-analysis aimed to assess the effects of Endocuff™/Endocuff Vision™-assisted colonoscopy (EAC) versus standard colonoscopy (SC) on ADR and other clinical, patient and resource-use outcomes. METHOD: MEDLINE, EMBASE, Web of Science, Scopus and the Cochrane Central Register of Controlled Trials were searched for full papers reporting randomized studies comparing EAC with SC. The primary outcome was ADR. Secondary outcomes comprised key polyp/adenoma detection, procedure-related, patient-related and health economic measures. Random effects meta-analyses provided pooled estimates of outcomes [risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CI)]. RESULTS: Twelve parallel-group randomized controlled trials (RCTs) and three crossover RCTs with data on 9140 patients were included. EAC significantly increased the ADR (RR 1.18, 95% CI 1.09-1.29), mean adenomas per procedure (MAP) (MD 0.19, 95% CI 0.06-0.33), polyp detection rate (PDR) (RR 1.20, 95% CI 1.10-1.30) and mean polyps per procedure (MPP) (MD 0.39, 95% CI 0.14-0.63) versus SC. EAC significantly increased segmental PDR versus SC in the sigmoid (RR 2.02, 95% CI 1.64-2.49), transverse (RR 1.63, 95% CI 1.09-2.42), ascending (RR 1.74, 95% CI 1.26-2.41) and caecal segments (RR 1.91, 95% CI 1.29-2.82). Procedure-related variables did not differ between arms. There were insufficient data for meta-analysis of health economic or patient-centred outcomes. CONCLUSIONS: EAC increased ADR, MAP, PDR and MPP versus SC without detrimental effects on procedure measures. Cost-effectiveness and patient experience data are lacking and would be valuable to inform practice recommendations.

Trial protocol for COLO-DETECT: A randomized controlled trial of lesion detection comparing colonoscopy assisted by the GI Genius™ artificial intelligence endoscopy module with standard colonoscopy.

AIM: Colorectal cancer is the second commonest cause of cancer death worldwide. Colonoscopy plays a key role in the control of colorectal cancer and, in that regard, maximizing detection (and removal) of pre-cancerous adenomas at colonoscopy is imperative. GI Genius™ (Medtronic Ltd) is a computer-aided detection system that integrates with existing endoscopy systems and improves adenoma detection during colonoscopy. COLO-DETECT aims to assess the clinical and cost effectiveness of GI Genius™ in UK routine colonoscopy practice. METHODS AND ANALYSIS: Participants will be recruited from patients attending for colonoscopy at National Health Service sites in England, for clinical symptoms, surveillance or within the national Bowel Cancer Screening Programme. Randomization will involve a 1:1 allocation ratio (GI Genius™-assisted colonoscopy:standard colonoscopy) and will be stratified by age category (<60 years, 60-<74 years, ≥74 years), sex, hospital site and indication for colonoscopy. Demographic data, procedural data, histology and post-procedure patient experience and quality of life will be recorded. COLO-DETECT is designed and powered to detect clinically meaningful differences in mean adenomas per procedure and adenoma detection rate between GI Genius™-assisted colonoscopy and standard colonoscopy groups. The study will close when 1828 participants have had a complete colonoscopy. An economic evaluation will be conducted from the perspective of the National Health Service. A patient and public representative is contributing to all stages of the trial. Registered at ClinicalTrials.gov (NCT04723758) and ISRCTN (10451355). WHAT WILL THIS TRIAL ADD TO THE LITERATURE?: COLO-DETECT will be the first multi-centre randomized controlled trial evaluating GI Genius™ in real world colonoscopy practice and will, uniquely, evaluate both clinical and cost effectiveness.

The COLO-COHORT (Colorectal Cancer Cohort) study: Protocol for a multi-centre, observational research study and development of a consent-for-contact research platform.

AIM: The COLO-COHORT study aims to produce a multi-factorial risk prediction model for colorectal neoplasia that can be used to target colonoscopy to those at greatest risk of colorectal neoplasia, ensuring that people are not investigated unnecessarily and maximizing the use of limited endoscopy resources. The study will also explore the link between neoplasia and the human gut microbiome. Additionally, the study aims to generate a cohort of colonoscopy patients who are 'research ready' through the development of a consent-for-contact (C4C) platform, to facilitate a range of colorectal cancer prevention studies to be conducted at scale and speed. METHODS AND ANALYSIS: This is a multi-centre observational study involving sites across the UK. Recruitment is over a 6-year period (2019-2025). Patients recruited to the study are those attending for colonoscopy. Patients are recruited into two groups, namely observational group A (10 000 patients) and C4C group B (10 000 patients), known as COLO-SPEED (Colorectal Cancer Screening Prevention Endoscopy and Early Diagnosis; https://colospeed.uk). Patients complete a health questionnaire, provide anthropometric measurements and submit biosamples (blood and stool-depending on the part of the study they are recruited into). Patients' colonoscopy and histology findings are also recorded. Models of factors associated with the presence of neoplasia at colonoscopy will be developed using logistic or multinomial regression. For internal validation, model discrimination and calibration will be assessed and bootstrapping and cross-validation approaches used. To enable long-term follow-up for outcomes related to colorectal cancer and polyps, patients are asked to consent to follow-up through data linkage with national databases. DISSEMINATION: In keeping with good research practice, following analysis by the study team the study investigators will make the anonymized dataset available to other researchers. The C4C platform will also be accessible to other researchers. The study findings will be submitted for publication in peer-reviewed journals and lay summaries will be disseminated to participants and the wider public.

Systematic review and meta-analysis: Associations between metabolic syndrome and colorectal neoplasia outcomes.

AIM: Metabolic syndrome (MetS) is a cluster of factors including obesity, hypertension, diabetes, hypercholesterolemia and hyperlipidaemia. It has been associated with an increased risk of colorectal neoplasia. This systematic review and meta-analysis assessed the association between MetS and (i) recurrence of adenomas or occurrence of CRC in patients with prior adenomas, and (ii) survival in patients with CRC. METHOD: MEDLINE, Embase, Scopus and Web of Science were searched up to 22 November 2019. Two authors independently conducted title and abstract screening; full text of eligible studies was evaluated. Where ≥3 studies reported effect measures for a specific outcome, meta-analysis using random effects model was conducted. I2 was used to assess between-study heterogeneity. Quality appraisal was undertaken with the Newcastle-Ottawa Score. RESULTS: The search identified 1,764 articles, 55 underwent full text screening, resulting in a total of 15 eligible studies. Five studies reported on metachronous neoplasia, with differing outcomes precluded a meta-analysis. No consistent relationship between MetS and metachronous neoplasia was found. Ten studies reported on survival outcomes. MetS was associated with poorer CRC-specific survival (HR = 1.8, 95% CI: 1.04-3.12, I2  = 92.7%, n = 3). Progression-free survival was also worse but this did not reach statistical significance (HR = 1.12, 95% CI: 0.89-1.42, I2  = 85.6%, n = 3). There was no association with overall survival (HR = 1.04, 95% CI: 0.94-1.15, I2  = 43.7%, n = 7). Significant heterogeneity was present but subgroup analysis did not account for this. CONCLUSION: MetS is associated with poorer CRC-specific survival, but evidence is inconsistent on metachronous neoplasia. Further research is warranted to better understand the impact of MetS on the adenoma-carcinoma pathway.

Barriers and facilitators to colonoscopy following fecal immunochemical test screening for colorectal cancer: A key informant interview study.

OBJECTIVES: People who are referred for colonoscopy, following an abnormal colorectal cancer (CRC) screening result, are at increased risk of CRC. Despite this, many individuals decline the procedure. The aim of this study was to investigate why. METHODS: As little is currently known about non-attendance at follow-up colonoscopy, and follow-up of abnormal screening results is a nurse-led process, we decided to conduct key informant interviews with Specialist Screening Practitioners ([SSPs] nurses working in the English Bowel Cancer Screening Program). Interviews were conducted online. Transcripts were assessed using inductive and deductive coding techniques. RESULTS: 21 SSPs participated in an interview. Five main types of barriers and facilitators to colonoscopy were described, namely: Sociocultural, Practical, Psychological, Health-related and COVID-related. Key psychological and sociocultural factors included: 'Fear of pain and discomfort associated with the procedure' and 'Lack of support from family and friends'. Key practical, health-related and COVID-related factors included: 'Family and work commitments', 'Existing health conditions as competing priorities' and 'Fear of getting COVID-19 at the hospital'. CONCLUSIONS: A range of barriers and facilitators to follow-up colonoscopy exist. Future studies conducted with patients are needed to further explore barriers to colonoscopy. PRACTICE IMPLICATIONS: Strategies to reduce non-attendance should adopt a multifaceted approach.

The Newcastle ENDOPREM™: a validated patient reported experience measure for gastrointestinal endoscopy.

OBJECTIVES: Measuring patient experience of gastrointestinal (GI) procedures is a key component of evaluation of quality of care. Current measures of patient experience within GI endoscopy are largely clinician derived and measured; however, these do not fully represent the experiences of patients themselves. It is important to measure the entirety of experience and not just experience directly during the procedure. We aimed to develop a patient-reported experience measure (PREM) for GI procedures. DESIGN: Phase 1: semi-structured interviews were conducted in patients who had recently undergone GI endoscopy or CT colonography (CTC) (included as a comparator). Thematic analysis identified the aspects of experience important to patients. Phase 2: a question bank was developed from phase 1 findings, and iteratively refined through rounds of cognitive interviews with patients who had undergone GI procedures, resulting in a pilot PREM. Phase 3: patients who had attended for GI endoscopy or CTC were invited to complete the PREM. Psychometric properties were investigated. Phase 4 involved item reduction and refinement. RESULTS: Phase 1: interviews with 35 patients identified six overarching themes: anxiety, expectations, information & communication, embarrassment & dignity, choice & control and comfort. Phase 2: cognitive interviews refined questionnaire items and response options. Phase 3: the PREM was distributed to 1650 patients with 799 completing (48%). Psychometric properties were found to be robust. Phase 4: final questionnaire refined including 54 questions assessing patient experience across five temporal procedural stages. CONCLUSION: This manuscript gives an overview of the development and validation of the Newcastle ENDOPREM™, which assesses all aspects of the GI procedure experience from the patient perspective. It may be used to measure patient experience in clinical care and, in research, to compare patients' experiences of different endoscopic interventions.

Uncovering undiagnosed liver disease: prevalence and opportunity for intervention in a population attending colonoscopy.

OBJECTIVE: Due to high rates of obesity and alcohol consumption, the prevalence of fatty liver disease is increasing. There is no widely adopted approach to proactively screen for liver disease in the community. We aimed to assess the burden of potentially undiagnosed liver disease in individuals attending for colonoscopy to develop a pathway to identify and manage individuals with undiagnosed liver disease. DESIGN: The OSCAR Study was a cross-sectional study recruiting patients attending for colonoscopy. Patients' metabolic and liver risk factors were measured. The prevalence of undiagnosed significant fatty liver disease was measured using the Fatty Liver Index (FLI) and Fibrosis-4 score (FIB-4). RESULTS: 1429 patients (mean age 59±14 years; 48.8% men) were recruited. 73.3% were overweight/obese, 12.7% had diabetes and 17.9% had metabolic syndrome. 19% were consuming more than recommenced alcohol levels (<14 units/week) and 41% had an AUDIT-C score ≥5. After excluding those with known liver disease, 43.2% of the cohort had a high FLI (high likelihood of fatty liver). 5.3% of these had a high FIB-4 score (>2.67, high probability of advanced fibrosis) and 90% of these were previously undiagnosed. 818 patients had a predicted 10-year cardiovascular event risk of ≥10%, however only 377 (46.1%) were on statin therapy. CONCLUSION: High levels of obesity, metabolic dysfunction and undiagnosed fatty liver disease were found in individuals attending for colonoscopy. Clinical encounters in the endoscopy unit may represent an opportunity to risk assess for liver and metabolic disease and provide an environment to develop targeted interventions.

Colorectal Cancer Screening and Surveillance for Non-Hereditary High-Risk Groups-Is It Time for a Re-Think?

PURPOSE OF REVIEW: Colorectal cancer (CRC) is the second most common cause of cancer death worldwide, killing approximately 900,000 people each year. An individual's risk of developing CRC is multi-factorial with known risk factors including increasing age, male sex, family history of CRC and raised body mass index. Population-based screening programmes for CRC exist in many countries, and in the United Kingdom (UK), screening is performed through the NHS Bowel Cancer Screening Programme (BCSP). Screening programmes offer a population-based approach for those at "average risk", and do not typically offer enhanced screening for groups at increased risk. In the UK, such patients are managed via non-screening symptomatic services but in a non-systematic way. RECENT FINDINGS: There is growing evidence that conditions such as cystic fibrosis and a history of childhood cancer are associated with higher risk of CRC, and surveillance of these groups is advocated by some organizations; however, national recommendations do not exist in most countries. SUMMARY: We review the evidence for screening "high risk" groups not covered within most guidelines and discuss health economic issues requiring consideration acknowledging that the demand on colonoscopy services is already overwhelming.

WASh multicentre randomised controlled trial: water-assisted sigmoidoscopy in English NHS bowel scope screening.

OBJECTIVES: The English Bowel Cancer Screening Programme invites 55 year olds for a sigmoidoscopy (Bowel Scope Screening (BSS)), aiming to resect premalignant polyps, thus reducing cancer incidence. A national patient survey indicated higher procedural pain than anticipated, potentially impacting on screening compliance and effectiveness. We aimed to assess whether water-assisted sigmoidoscopy (WAS), as opposed to standard CO2 technique, improved procedural pain and detection of adenomatous polyps. DESIGN: The WASh (Water-Assisted Sigmoidoscopy) trial was a multicentre, single-blind, randomised control trial for people undergoing BSS. Participants were randomised to either receive WAS or CO2 from five sites across England. The primary outcome measure was patient-reported moderate/severe pain, as assessed by patients on a standard Likert scale post procedure prior to discharge. The key secondary outcome was adenoma detection rate (ADR). The costs of each technique were also measured. RESULTS: 1123 participants (50% women, mean age 55) were randomised (561 WAS, 562 CO2). We found no difference in patient-reported moderate/severe pain between WAS and CO2 (14% in WAS, 15% in CO2; p=0.47). ADR was 15% in the CO2 arm and 11% in the WAS arm (p=0.03); however, it remained above the minimum national performance standard in both arms. There was no statistical difference in mean number of adenomas nor overall polyp detection rate. There was negligible cost difference between the two techniques. CONCLUSION: In the context of enema-prepared unsedated screening sigmoidoscopies performed by screening-accredited endoscopists, no difference in patient-reported pain was seen when using either a CO2 or WAS intubation technique. TRIAL REGISTRATION NUMBER: ISRCTN81466870.