The use of indigocarmine spray increases the colonoscopic detection rate of adenomas

Purpose  It remains controversial whether chromocolonoscopy using indigocarmine increases the detection of colorectal polyps. We aimed to assess the impact of indigocarmine dye spray on the detection rate of adenomas and the feasibility of learning the technique in a Western practice. Methods  400 patients were prospectively allocated into 2 groups; A (n = 200): indigocarmine chromocolonoscopy was performed by a Japanese colonoscopist with expertise in chromoscopy; B (n = 200): initial 100 patients (B-1), a Western colonoscopist with no previous experience of chromoscopy performed conventional colonoscopy, but with at least 10 min observation during colonoscopy withdrawal. In the next 100 patients (B-2), he performed chromocolonoscopy. All polyps found were resected. Regression analysis was used to compare the numbers of polyps detected in groups A, B-1 and B-2, whilst controlling for gender, age, indication and history of colorectal cancer. Results  There were significant differences in the numbers of neoplastic polyps and flat adenomas between groups A and B-1 as well as between B-1 and B-2, but not between A and B-2. There was no significant difference in numbers of advanced lesions. Chromocolonoscopy (A and B-2) detected more neoplastic polyps of ≤5 mm. Conclusion  Chromocolonoscopy increases the detection of neoplastic polyps and flat adenomas, particularly diminutive polyps, but does not increase the detection of advanced lesions.     

Retrograde inspection vs standard forward view for the detection of colorectal adenomas during colonoscopy: A back-to-back randomized clinical trial

BACKGROUND The adenoma detection rate(ADR) is inversely associated with the incidence of interval colorectal cancer and serves as a benchmark quality criterion during screening colonoscopy. However, adenoma miss rates reach up to 26% and studies have shown that a second inspection of the right colon in retroflected view(RFV) can increase ADR.AIM To assess whether inspection of the whole colon in RFV compared to standard forward view(SFV) can increase ADR.METHODS Patients presenting for screening or surveillance colonoscopy were invited to participate in this randomized controlled trial and randomized into two arms. In RFV arm colonoscopy was initially performed with SFV, followed by a second inspection of the whole colon in RFV. In the SFV arm first withdrawal was performed with SFV, followed by a second inspection of the whole colon again with SFV. Number, size and morphology of polyps found during first and second inspection in each colonic segment were recorded and all polyps were removed and sent for histopathology in separate containers.RESULTS Two hundred and five patients were randomly assigned to the RFV(n = 101) and SFV(n = 104) arm. In the RFV arm, both polyp detection rate(PDR) and ADR were increased under second inspection in RFV(PDR 1~(st) SFV: 39.8%, PDR 2~(nd)RFV: 46.6%; ADR 1~(st) SFV: 35.2%, ADR 2~(nd) RFV: 42%). Likewise, in the SFV arm,PDR and ADR were increased under second inspection(PDR 1~(st) SFV: 37.5%, PDR 2~(nd) SFV: 46.6%; ADR 1~(st) SFV: 34.1%, ADR 2~(nd)SFV: 44.3%) with no significant differences in ADR and PDR between the SFV and RFV arm. Mean number of adenomas per patient(APP) was increased in the RFV and SFV(APP RFV arm: 1~(st) SFV: 1.71; 2~(nd) RFV: 2.38; APP SFV arm: 1~(st) SFV: 1.83, 2~(nd)SFV:2.2). The majority of adenomas additionally found during second inspection in RFV or in SFV were located in the transverse and left-sided colon and were 5 mm in size.CONCLUSION Second inspection of the whole colon leads to increased adenoma detection with no differences between SFV and RFV. Hence, increased detection is most likely a feature of the second inspection itself but not of the inspection mode.     

Technological advances for improving adenoma detection rates: The changing face of colonoscopy

Worldwide, colorectal cancer is the third commonest cancer. Over 90% follow an adenoma-to-cancer sequence over many years. Colonoscopy is the gold standard method for cancer screening and early adenoma detection. However, considerable variation exists between endoscopists’ detection rates. This review considers the effects of different endoscopic techniques on adenoma detection. Two areas of technological interest were considered: (1) optical technologies and (2) mechanical technologies. Optical solutions, including FICE, NBI, i-SCAN and high definition colonoscopy showed mixed results. In contrast, mechanical advances, such as cap-assisted colonoscopy, FUSE, EndoCuff and G-EYE™, showed promise, with reported detections rates of up to 69%. However, before definitive recommendations can be made for their incorporation into daily practice, further studies and comparison trials are required.     

Improved detection of colorectal neoplasms with selective use of chromoendoscopy in 2005 consecutive patients

Background Colorectal cancer mortality is decreased by endoscopic polypectomy, but conventional colonoscopy may be inadequate for detecting subtle colonic lesions. Methods We selectively performed chromoendoscopy in all patients undergoing colonoscopy between January 1999 and December 2005 at the International Health Union of Rome. Patients with a history of colorectal polyps, inflammatory bowel disease, colorectal surgery or coagulopathy and those with poor bowel preparation were excluded from this analysis. Whenever colonoscopy revealed suspicious mucosal areas, dye-spraying with 0.2% indigo carmine solution was also performed. Findings from conventional and dyespraying views were classified morphologically, and specimens were analyzed histologically. Non-adenomatous lesions were classified as negative findings. Results A total of 2005 patients underwent conventional colonoscopy and in 305 cases (15%) chromoendoscopy was also performed. Conventional colonoscopy identified 508 neoplasms in 381 patients (19%). Selective chromoendoscopy found an additional 244 neoplasms in 212 patients (11%). Thus, chromoendoscopy was positive in 212 (70%) of 305 patients in whom the examination was performed. Overall, 56 large, ulcerated, advanced cancers and 696 non-advanced neoplasms were found. Of the 696 nonadvanced neoplasms, 448 (65%) were polypoid and 248 (35%) were non-polypoid. All but 4 non-polypoid lesions were only detected with chromoendoscopy. Of the 248 non-polypoid lesions, 12 (5%) were depressed and 236 (95%) were flat. Advanced histology was present in 39 non-polypoid lesions (15%) and was more common in depressed lesions than in flat ones (58% vs. 13%; p<0.001). Conclusions Our study confirms the existence of flat and depressed neoplasms in an Italian population. The vast majority of non-polypoid lesions were only detected by chromoendoscopy, and many lesions with advanced histology were missed by conventional colonoscopy. We therefore recommend selectively performing chromoendoscopy when conventional colonoscopy provides clues for non-polypoid lesions. Therefore, endoscopists should be trained in the detection of these subtle mucosal clues, as well as in the use of chromoendoscopy to enhance their detection. An erratum to this article is available at .     

Conventional colonoscopy and magnified chromoendoscopy for the endoscopic histological prediction of diminutive colorectal polyps： A single operator study

AIM: To accurately differentiate the adenomatous from the non-adenomatous polyps by colonoscopy. METHODS: All lesions detected by colonoscopy were first diagnosed using the conventional view followed by chromoendoscopy with magnification. The diagnosis at each step was recorded consecutively. All polyps were completely removed endoscopically for histological evaluation. The accuracy rate of each type of endoscopic diagnosis was evaluated, using histological findings as gold standard. RESULTS: A total of 240 lesions were identified, of which 158 (65.8%) were non-neoplastic and 82 (34.2%) were adenomatous. The overall diagnostic accuracy of conventional view, and chromoendoscopy with magnification was 76.3% (183/240) and 95.4% (229/240), respectively (P< 0.001) CONCLUSION: The combination of colonoscopy and magnified chromoendoscopy is the most reliable non-biopsy method for distinguishing the non-neoplastic from the neoplastic lesions.     

Colorectal cancer screening: Results of a 5-year program in asymptomatic subjects at increased risk

BACKGROUND AND AIMS: The province of Ferrara has one of the highest incidences of colorectal cancer (CRC) in Italy. In January 2000, we set up a colonoscopy screening program focussing on first-degree relatives of CRC patients. We now report the results 5 years after the beginning of the project. SCREENEES AND METHODS: In October 1999, we started a campaign stressing the usefulness of colonoscopy for the first-degree relatives of CRC patients. Subjects included in the screening program were aged between 45 and 75 years with at least one first-degree relative affected by CRC. They were invited to an interview where a physician suggested colonoscopy as a screening option. RESULTS: In 5 years, 776 subjects were interviewed and 733 (94.4%) agreed to an endoscopic examination (M/F:375/401; mean age 55 years): 562 colonoscopies were performed. Adenomas and cancers were found in 122 (21.7%) and 12 (2.1%) subjects, respectively. Histological examination in 181 persons with lesions (32.8%) showed (most serious lesion quoted) 47 hyperplastic polyps (26% of all lesions), 2 serrated adenomas (1.1%), 68 tubular adenomas (48%), 24 tubulovillous adenomas (13.3%), 9 adenomas with high grade dysplasia (5%) and 12 adenocarcinomas (6.6%). The majority of the cancers were at an early stage (8 Dukes A and 3 Dukes B). Sedation was used in only 42 colonoscopies (7.5%). CONCLUSIONS: A colonoscopy-based screening in this selected high-risk population is feasible. Even without sedation subjects readily agreed to the endoscopic procedure. We identified a significant number of advanced neoplasms and cancers at an early stage suggesting that this could be a useful tool in early identification of CRC.     

Narrow band imaging vs. high definition colonoscopy for detection of colorectal adenomas in patients with positive faecal occult blood test: A randomised trial

BackgroundThe impact of narrow band imaging in improving the adenoma detection rate in a screening scenario is still unclear.AimTo evaluate whether narrow band imaging compared with high definition white light colonoscopy can enhance the adenoma detection rate during screening colonoscopy.MethodsConsecutive patients presenting for screening colonoscopy were included into this study and were randomly assigned to the narrow band imaging group (Group 1) or standard colonoscopy group (Group 2). Primary end point was the adenoma detection rate and secondary aim was the detection rate of advanced adenomas.ResultsOverall, 117 patients were allocated to Group 1 and 120 to Group 2. Both the adenoma detection rate and the detection rate of advanced adenomas were not significantly different between the two groups (respectively, 52.1% vs. 55%, RR = 0.95, 95% CI 0.75–1.20; 32.5% vs. 44.2%, RR = 0.74, 95% CI 0.53–1.02). No significant difference between the proportions of polypoid and flat adenomas was found. Male gender, no prior history of screening, and endoscopist's adenoma detection rate were independent predictive factors of higher advanced adenoma detection rate.ConclusionsIn a screening scenario, narrow band imaging did not improve the adenoma nor advanced adenoma detection rates compared to high definition white light colonoscopy.     

Real-life chromoendoscopy for dysplasia surveillance in ulcerative colitis

AIM To evaluate the use of chromoendoscopy for surveillance of ulcerative colitis in a real-life community hospital setting.METHODS Patients with extensive ulcerative colitis, having disease duration of more than 8 years and who presented between the years of 1999 to 2013, were offered enrolment in this single cohort prospective study. All participants underwent standard bowel preparation with sodium phosphate and chromoendoscopy. Two expert endoscopists, novice to chromoendoscopy, evaluated each segment of the colon with standarddefinition colonoscopes after spray application of 0.4% indigo carmine. All observed lesions were recorded and evaluated before being removed and/or biopsied. In addition, nontargeted biopsies were taken from each segment of the colon. The dysplasia detection rate and dysplasia detection yield were ascertained. RESULTS A total of 21 neoplastic lesions(2 carcinomas, 4 of high-grade dysplasia and 15 of low-grade dysplasia) and 27 nondysplastic lesions were detected in 16 of the total 67 patients(70% male; median disease duration: 17 years; median age at diagnosis: 25 years; 92% aminosalicylate-treated). The dysplasia detection rate was 10.5%(7/67 patients). The dysplasia detection yield was 20.8%(10/48) for targeted biopsies and 3.5%(11/318) for nontargeted biopsies. The sensitivity and specificity for the macroscopic evaluation of neoplasia using chromoendoscopy were 48% [95% confidence interval(CI): 26%-70%] and 96%(95%CI: 93%-98%), respectively. The positive predictive and negative predictive values were 42%(95%CI: 27%-59%) and 97%(95%CI: 95%-98%), respectively. A total of 19/21 dysplastic lesions were detected in mucosa with histologic inflammation.CONCLUSION Chromoendoscopy seems to be of value for dysplasia surveillance of ulcerative colitis in a community hospital setting. The yield of non-targeted biopsies is negligible.     

Factors affecting the quality of bowel preparation for colonoscopy in hard-to-prepare patients: Evidence from the literature

Adequate bowel cleansing is critical for a high-quality colonoscopy because it affects diagnostic accuracy and adenoma detection. Nevertheless, almost a quarter of procedures are still carried out with suboptimal preparation, resulting in longer procedure times, higher risk of complications, and higher likelihood of missing lesions. Current guidelines recommend high-volume or low-volume polyethylene glycol(PEG)/non-PEG-based split-dose regimens. In patients who have had insufficient bowel cleans...     

When should we perform colonoscopy to increase the adenoma detection rate?

The rate of adenoma detection is the most reliable quality indicator of colonoscopy. Studies have reported that colonoscopy performed in morning has a higher adenoma detection rate (ADR) than that performed in the afternoon. These studies have explained that several physician-related factors such as undergoing an emergency procedure the night before colonoscopy, accumulated workload, and increased fatigue level in the afternoon might have led to such finding. However, several opposing articles have indicated that the time of day and ADR is not quite related. Complex confounding factors can impact study results. Colonoscopy withdrawal time and bowel preparation quality are key factors. However, queue list numbers, participation of academic fellows, nurses' assistance, and the number of colonoscopies allocated per hour are also notable factors. Recently, an attempt has been made to homogenize the ADR in the morning and afternoon through artificial intelligence-assisted colonoscopy. This review article introduces the history of this long-debated topic, discusses points to consider in real-world practice, and suggests new ideas for planning future research. By understanding this issue, the rate of adenoma detection during colonoscopy is expected to be improved further.     

New technologies and techniques to improve adenoma detection in colonoscopy

Adenoma detection rate (ADR) is a key component of colonoscopy quality assessment, with a direct link between itself and future mortality from colorectal cancer. There are a number of potential factors, both modifiable and non-modifiable that can impact upon ADR. As methods, understanding and technologies advance, so should our ability to improve ADRs, and thus, reduce colorectal cancer mortality. This article will review new technologies and techniques that improve ADR, both in terms of the endoscopes themselves and adjuncts to current systems. In particular it focuses on effective techniques and behaviours, developments in image enhancement, advancement in endoscope design and developments in accessories that may improve ADR. It also highlights the key role that continued medical education plays in improving the quality of colonoscopy and thus ADR. The review aims to present a balanced summary of the evidence currently available and does not propose to serve as a guideline.     

Técnicas colonoscópicas para la detección de pólipos: un estudio egipcio

Introduction and aimsThe polyp detection rate (PDR) is defined as the percentage of colonoscopies in which one or more polyps are detected, and has been shown to be highly correlated with the adenoma detection rate. The aim of the present study was to evaluate the PDR at the Endoscopy Unit of the Kasr Al-Ainy Hospital, Cairo University, Egypt, through the i-SCAN, Endocuff, and underwater colonoscopy techniques.Materials and methodsThe study was conducted on 100 Egyptian subjects over 50 years of age. Their polyp detection rate was measured through 4 different colonoscopic techniques. An equal number of patients were divided into 4 groups: i-SCAN, Endocuff, underwater colonoscopy, and controls. The control group was examined using standard white light colonoscopy. The colonoscopy evaluation included the type of agent utilized for bowel preparation, preparation grade, and colonoscopy withdrawal time.ResultsThe general PDR was 48%. The i-SCAN technique had the highest rate (56%), followed by the underwater (52%) and the Endocuff (48%) techniques.ConclusionThe i-SCAN and underwater colonoscopy techniques produced higher PDR than the Endocuff-assisted and standard techniques, but with no statistical significance.     

Endoscopy Nurse Participation May Increase the Polyp Detection Rate by Second-Year Fellows during Screening Colonoscopies

Background/Aims

The aim of this study was to assess the effects of endoscopy nurse participation on polyp detection rate (PDR) and adenoma detection rate (ADR) of second-year fellows during screening colonoscopies.

Methods

This was a single-center, prospective, randomized study comparing a fellow alone and a fellow plus an endoscopy nurse as an additional observer during afternoon outpatient screening colonoscopies. The primary end points were PDR and ADR.

Results

One hundred ninety-one colonoscopies performed by a fellow alone and 192 colonoscopies performed by a fellow plus an endoscopy nurse were analyzed. The PDR was significantly higher when the nurse was involved (53.1% vs. 41.3%, p<0.05); however, there was no significant difference in the ADR between the two groups (38.5% vs. 29.8%, p=0.073). There was no difference in the percentage of patients with ≥2 polyps, advanced adenomas, polyp size, polyp location, and polyp shapes between the two groups. There was no difference in the PDR according to the level of experience of the endoscopy nurse.

Conclusions

Endoscopy nurse participation as an additional observer during screening colonoscopy performed by second-year fellow increases the PDR; however, the level of experience of the nurse was not an important factor.     

Indications and outcomes of endoscopic resection for non-pedunculated colorectal lesions: A narrative review

In the last years, endoscopic techniques gained a crucial role in the treatment of colorectal flat lesions. At the same time, the importance of a reliable assessment of such lesions to predict the malignancy and the depth of invasion of the colonic wall emerged. The current unsolved dilemma about the endoscopic excision techniques concerns the necessity of a reliable submucosal invasive cancer assessment system that can stratify the risk of the post-procedural need for surgery. Accordingly, this narrative literature review aims to compare the available diagnostic strategies in predicting malignancy and to give a guide about the best techniques to employ. We performed a literature search using electronic databases (MEDLINE/PubMed, EMBASE, and Cochrane Library). We collected all articles about endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) registering the outcomes. Moreover, we analyzed all meta-analyses comparing EMR vs ESD outcomes for colorectal sessile or non-polypoid lesions of any size, preoperatively estimated as non-invasive. Seven meta-analysis studies, mainly Eastern, were included in the analysis comparing 124 studies and overall 22954 patients who underwent EMR and ESD procedures. Of these, eighty-two were retrospective, twenty-four perspective, nine case-control, and six cohorts, while three were randomized clinical trials. A total of 18118 EMR and 10379 ESD were completed for a whole of 28497 colorectal sessile or non-polypoid lesions > 5-10 mm in size. In conclusion, it is crucial to enhance the preoperative diagnostic workup, especially in deciding the most suitable endoscopic method for radical resection of flat colorectal lesions at risk of underlying malignancy. Additionally, the ESD necessitates further improvement because of the excessively time-consuming as well as the intraprocedural technical hindrances and related complications. We found a higher rate of en bloc resections and R0 for ESD than EMR for non-pedunculated colorectal lesions. Nevertheless, despite the lower local recurrence rates, ESD had greater perforation rates and needed lengthier procedural times. The prevailing risk for additional surgery in ESD rather than EMR for complications or oncologic reasons is still uncertain.     

Diphyllobothrium latum： A case of an incidental finding

Colorectal cancer screening can be performed by fecal occult blood testing, sigmoidoscopy, double contrast barium enema or colonoscopy. Colonoscopy has the significant advantage that polyps can be removed during the same procedure. Occasionally, colonoscopy can also reveal unexpected findings, including parasitic infections, even in asymptomatic patients. Tapeworms or cestodes are hermaphroditic parasites, which can live for considerable periods of time in the human gastrointestinal tract. Fish tapeworm （Diphyllobothrium species） are endemic in various parts of the world, the commonest species being Diphyllobothrium latum. Humans are the main definitive host for D. Latum and the majority of individuals harbouring the parasite are asymptomatic, while 40% of infected individuals may have low vitamin B12 levels. We describe a case of D. latum infection found on routine colonoscopic screening for colorectal cancer in an asymptomatic patient, which was successfully treated with praziquantel. The infection likely arose following raw fish （sushi） consumption.     

Inter-centre variability of the adenoma detection rate: A prospective,multicentre study

Background

Suboptimal colonoscopy quality is related to a higher risk of interval cancer. Aim of our study was to explore the variability in detection rate of neoplasia among different endoscopic centres in an unselected population.

Methods

Consecutive patients referred for colonoscopy in 28 Italian centres were included. Detection rate for polyp, neoplasia and advanced neoplasia was assessed at both the individual and centre level. Inter-centre variability in detection rate of colorectal lesions was explored after adjusting for patient-related factors at multivariate analysis.

Results

3150 patients were included. Median detection rates for polyp, neoplasia and advanced neoplasia were 35%, 26% and 13%. At multivariate analysis, patient-related factors associated with neoplasia detection were age, sex, alcohol and smoking history. After adjusting for these variables, a statistically significant difference in the observed/expected ratio among different centres was observed (Chi-squared test: p < 0.01). Among non-patient-related factors, documentation of withdrawal time was associated with neoplasia detection. However, a statistically significant inter-centre variability also remained after adjusting for this variable.

Conclusions

A wide variability was present in the detection rate of neoplasia and advanced neoplasia at the level of endoscopic centres in an unselected population. The adoption of a centre-related neoplasia detection rate could be suggested as a performance indicator.     

放大内镜结合染色内镜对早期大肠癌及其癌前病变的诊断和治疗

放大内镜结合染色内镜通过对早期大肠癌及其癌前病变的表面腺管开口的辨别,可以大致预测黏膜病变的病理组织学类型,对大肠黏膜病变作出实时准确的判断,不仅提高了大肠癌的早期诊断率,而且为病变的内镜下正确处理提供了快速而准确的依据,从而指导大肠癌及其癌前病变的治疗。     

定期反馈对结直肠癌机会性筛查中 腺瘤检出率的影响

目的探索在全结肠镜检查行结直肠癌机会性筛查中实行腺瘤检出率（adenoma detection rate,ADR）定期反馈制度是否可提高内镜医师ADR。方法本研究为观察性研究,研究分为3个阶段：干预前的基线阶段（简称干预前）、定期反馈阶段（简称干预期）和干预后阶段（简称干预后）。干预前：回顾2017年6月—2018年5月在首都医科大学附属北京世纪坛医院消化内科进行结直肠癌机会性筛查的所有患者资料,计算每名内镜医师的ADR。干预期：2018年6月—2018年11月由参与反馈的内镜医师对结直肠癌机会性筛查的患者进行全结肠镜检查,每个月初计算每名内镜医师前一个月的ADR并以报告单的形式提供反馈。干预后：2018年12月—2019年1月由参与反馈的内镜医师对结直肠癌机会性筛查的患者进行全结肠镜检查,计算反馈干预停止后每名内镜医师的ADR。比较3个阶段的ADR和息肉检出率（polyp detection rate,PDR）。结果干预前、干预期和干预后分别纳入1 768例、1 308例和344例结直肠癌机会性筛查患者。共有8名内镜医师参与研究全过程。总ADR从干预前的23.70%（419/1 768）升高至干预期的33.72%（441/1 308）（χ2=37.449,P＜0.05）。干预后2个月,ADR轻度下降至33.14%（114/344）,但与干预前相比,仍然升高（χ2=13.602,P＜0.05）。总PDR从干预前的47.17%（834/1 768）提高至干预期的52.68%（689/1 308）,两者相比差异有统计学意义（χ2=9.111,P＜0.05）。停止干预后,PDR轻度上升至53.78%（185/344）,与干预前相比差异有统计学意义（χ2=5.035,P＜0.05）。结论在结直肠癌机会性筛查中,对内镜医师进行ADR的定期反馈可以提高结直肠ADR。     

Prevalence of Proximal Neoplasms Among Asymptomatic Patients According to Distal Colorectal Findings

Colorectal cancer has been described in association with hyperplastic polyposis. Only half of proximal colon cancers are associated with distal adenomas. To compare the prevalence of proximal and advanced neoplasia between patients with distal hyperplastic polyps only; with distal adenomas with or without hyperplastic polyps; and with no distal polyps, we retrospectively analyzed data of 1,064 adults who underwent colonoscopy. Of these patients, 3% had neoplasia. Proximal neoplasia occurred in 0.8% of 945 patients with no distal polyps, compared to none of 19 with distal hyperplastic polyps (P > 0.05) and 6% with distal adenomas (P > 0.05). Proximal advanced neoplasia occurred in 0.6% patients with no distal polyps, compared with none with distal hyperplastic polyps (P > 0.05) and 6% with distal adenomas (P > 0.05). In conclusion, patients with distal hyperplastic polyps, unlike those with distal adenomas, do not exhibit an increased risk for proximal neoplasia or proximal advanced neoplasia compared to those with no distal polyps.     

Short turn radius colonoscope in an anatomical model: Retroflexed withdrawal and detection of hidden polyps

AIM: To evaluate the new Retro View~(TM) colonoscope and compare its ability to detect simulated polyps "hidden" behind colonic folds with that of a conventional colonoscope, utilizing anatomic colon models.METHODS: Three anatomic colon models were prepared,with twelve simulated polyps "hidden" behind haustral folds and five placed in easily viewed locations in each model. Five blinded endoscopists examined two colon models in random order with the conventional or Retro View~(TM) colonoscope, utilizing standard withdrawal technique. The third colon model was then examined with the Retro View~(TM) colonoscope withdrawn initially in retroflexion and then in standard withdrawal. Polyp detection rates during standard and retroflexed withdrawal of the conventional and Retro View~(TM) colonoscopes were determined. Polyp detection rates for combined standard and retroflexed withdrawal(combination withdrawal) with the Retro View~(TM) colonoscope were also determined.RESULTS: For hidden polyps, retroflexed withdrawal using the Retro View~(TM) colonoscope detected more polyps than the conventional colonoscope in standard withdrawal(85% vs 12%, P = 0.0001). For hidden polyps, combination withdrawal with the Retro View~(TM) colonoscope detected more polyps than the conventional colonoscope in standard withdrawal(93% vs 12%, P ≤ 0.0001). The Retro View~(TM) colonoscope in "combination withdrawal" was superior to other methods in detecting all(hidden + easily visible) polyps, with successful detection of 80 of 85 polyps(94%) compared to 28(32%) polyps detected by the conventional colonoscope in standard withdrawal(P 0.0001) and 67(79%) polyps detected by the Retro View~(TM) colonoscope in retroflexed withdrawal alone(P 0.01). Continuous withdrawal of the colonoscope through the colon model while retroflexed was achieved by all endoscopists. In a post-test survey, four out of five colonoscopists reported that manipulation of the colonoscope was easy or very easy.CONCLUSION: In simulated testing, the Retro View~(TM) colonoscope increased detection of hidden polyps. Combining standard withdrawal with retroflexed withdrawal may become the new paradigm for "complete screening colonoscopy".