Polyps In Colonoscopy Research Articles

Colonoscopic Polyp Classification Using Local Shape and Texture Features

In this paper, a method is proposed for colonic polyp classification which can perform a virtual biopsy for assessing the stage of malignancy in polyps. Geometry, texture, and colour of a polyp give sufficient cue of its nature. The proposed framework characterizes geometry or shape of a polyp by pyramid histogram of oriented gradient (PHOG) features. To encapsulate the texture of the polyp surface, a fractal weighted local binary pattern (FWLBP) descriptor is employed, which is robust to affine transformation. It is also partially robust to illumination variations which is generally encountered during endoscopy. The optimal feature fusion is done using a feature ranking algorithm based on fuzzy entropy. Finally, to evaluate the classification performance of the proposed model, kernel-based support vector machines (SVM) and RUSBoosted tree are used. Experimental results carried on two databases clearly indicate that the proposed method can be used in the colonoscopic polyps classification. The proposed method can give polyp classification accuracies of 90.12% and 84.1%, and AUC of 0.91 and 0.92 for publicly available database and our own database, respectively.

Assessing perspectives on artificial intelligence applications to gastroenterology

Assessing perspectives on artificial intelligence applications to gastroenterology

Endoscopic Recognition and Management Strategies for Malignant Colorectal Polyps: Recommendations of the US Multi-Society Task Force on Colorectal Cancer.

Endoscopic Recognition and Management Strategies for Malignant Colorectal Polyps: Recommendations of the US Multi-Society Task Force on Colorectal Cancer.

Is artificial intelligence the final answer to missed polyps in colonoscopy?

Lesions missed by colonoscopy are one of the main reasons for post-colonoscopy colorectal cancer, which is usually associated with a worse prognosis. Because the adenoma miss rate could be as high as 26%, it has been noted that endoscopists with higher adenoma detection rates are usually associated with lower adenoma miss rates. Artificial intelligence (AI), particularly the deep learning model, is a promising innovation in colonoscopy. Recent studies have shown that AI is not only accurate in colorectal polyp detection but can also reduce the miss rate. Nevertheless, the application of AI in real-time detection has been hindered by heterogeneity of the AI models and study design as well as a lack of long-term outcomes. Herein, we discussed the principle of various AI models and systematically reviewed the current data on the use of AI on colorectal polyp detection and miss rates. The limitations and future prospects of AI on colorectal polyp detection are also discussed.

Deep learning to find colorectal polyps in colonoscopy: A systematic literature review.

Colorectal cancer has a great incidence rate worldwide, but its early detection significantly increases the survival rate. Colonoscopy is the gold standard procedure for diagnosis and removal of colorectal lesions with potential to evolve into cancer and computer-aided detection systems can help gastroenterologists to increase the adenoma detection rate, one of the main indicators for colonoscopy quality and predictor for colorectal cancer prevention. The recent success of deep learning approaches in computer vision has also reached this field and has boosted the number of proposed methods for polyp detection, localization and segmentation. Through a systematic search, 35 works have been retrieved. The current systematic review provides an analysis of these methods, stating advantages and disadvantages for the different categories used; comments seven publicly available datasets of colonoscopy images; analyses the metrics used for reporting and identifies future challenges and recommendations. Convolutional neural networks are the most used architecture together with an important presence of data augmentation strategies, mainly based on image transformations and the use of patches. End-to-end methods are preferred over hybrid methods, with a rising tendency. As for detection and localization tasks, the most used metric for reporting is the recall, while Intersection over Union is highly used in segmentation. One of the major concerns is the difficulty for a fair comparison and reproducibility of methods. Even despite the organization of challenges, there is still a need for a common validation framework based on a large, annotated and publicly available database, which also includes the most convenient metrics to report results. Finally, it is also important to highlight that efforts should be focused in the future on proving the clinical value of the deep learning based methods, by increasing the adenoma detection rate.

Suction marking method: a novel technique to prevent overlookingof polyps detected upon endoscope insertion.

Suction marking method: a novel technique to prevent overlookingof polyps detected upon endoscope insertion.

Automated polyp segmentation for colonoscopy images: A method based on convolutional neural networks and ensemble learning.

To automatically and efficiently segment the lesion area of the colonoscopy polyp image, a polyp segmentation method has been presented. An ensemble model of pretrained convolutional neural networks was proposed, using Unet-VGG, SegNet-VGG, and PSPNet. Firstly, the Unet-VGG is obtained by the first 10 layers of VGG16 as the contraction path of the left half of the Unet. Then, the SegNet-VGG is acquired by fine-tuned transfer learning VGG16, using the first 13 layers of VGG16 as the encoder of the SegNet and combined the original decoder of the SegNet. By adjusting the input size of the Unet-VGG, SegNet-VGG, and PSPNet, the preprocessed data can be correctly fed to the three network models. The three models are used as the basic trainer to train and segment the datasets. Based on the ensemble learning algorithm, the weight voting method is used to ensemble the segmentation results corresponding to single basic trainer. Both IoU and DICE similarity score were used to evaluate the segmentation quality for cvc300 with 300 images, CVC-ClinicDB with 612 images, and ETIS-LaribPolypDB with 196 images. From the experimental results, the IoU and DICE obtained by the proposed method for the cvc300 datasets can reach up to 96.16% and 98.04%, respectively, the IoU and DICE for the CVC-ClinicDB datasets can reach up to 96.66% and 98.30%, respectively, whereas the IoU and DICE for the ETIS-LaribPolypDB datasets can reach up to 96.95% and 98.45%, respectively. Evaluation of the IoU and DICE in our methods shows higher accuracy than previous methods. The experimental results show that the proposed method improved correspondingly in IoU and DICE compared to a single basic trainer. The range of improvement is 1.98%-6.38%. The proposed ensemble learning succeeds in automatic polyp segmentation, which potentially helps to establish more polyp datasets.

550 Discordance in Colorectal Polyp Size Determination Between Colonoscopy and Pathology Reporting

INTRODUCTION: National guidelines recommend that patients with colorectal adenomas ≥1cm undergo surveillance colonoscopy to prevent colorectal cancer. Polyp size is often assessed twice, once during colonoscopy and again during pathology examination. It remains unclear whether these measurements vary and which should govern surveillance intervals. METHODS: We retrospectively analyzed a random sample of primary care patients who underwent polypectomy between January 1, 2013 and January 1, 2016 in a large academic healthcare center. Chart abstractors reviewed electronic health record data for colonoscopic polyp descriptors and measurements, corresponding pathology measurements, and histology. We excluded cases with normal histology, missing pathology, fragments, unreliable polyp matches between reports, and >5 polypectomies. We performed a paired t-test to assess polyp size discordance between reports and calculated Cohen's kappa coefficient to assess agreement whether the size was ≥1 cm. RESULTS: We reviewed 1,528 patient charts, and 831 (54.4%) met inclusion criteria, representing 1,532 polyps. Sizes ranged from 0.1-3.0cm on colonoscopy and 0.1-2.7cm on pathology reports. On colonoscopy report, the majority (881, 57.5%) used only a descriptive term rather than a numeric value to describe size (Table 1). Descriptive size terms were diminutive (513), tiny (39), small (328), and large (1). Only 2.8% of polyps described as diminutive, small, or tiny on the colonoscopy report were ≥1cm on the corresponding pathology report. Among the 367 (24.0%) polyps with discrete numeric sizes on both reports, size discordance varied by >0.2 cm for 50% of polyps (Figure 1). More of these polyps were ≥1 cm on colonoscopy (70) than on pathology (51) report, and there was remarkable clustering at 1 cm by colonoscopy report estimation (Figure 2). There was moderate agreement (kappa = 0.52) on size ≥1 cm. Among tubular adenomas (TA) ≥1 cm on colonoscopy or pathology report (36), 10 (27.8%) were ≥1 cm on both, 18 (50.0%) were ≥1 cm on colonoscopy only, and 8 (22.2%) were ≥1 cm on pathology only. CONCLUSION: There is considerable discordance between colonoscopic and pathology polyp size measurements, with more polyps sized as ≥1 cm by colonoscopic estimation compared to pathology, which has implications for surveillance frequency. Future studies should investigate the implications of discordant measurements on clinical outcomes and inform guidelines on surveillance intervals.

Real-time automatic detection system increases colonoscopic polyp and adenoma detection rates: a prospective randomised controlled study

ObjectiveThe effect of colonoscopy on colorectal cancer mortality is limited by several factors, among them a certain miss rate, leading to limited adenoma detection rates (ADRs). We investigated the effect...

An Adaptive Regularization Approach to Colonoscopic Polyp Detection Using a Cascaded Structure of Encoder–Decoders

This research aims to segment colonoscopic images by automatically extracting polyp features by exploiting the strengths of convolution neural networks (CNN). The proposed model employs deep learning and adaptive regularization techniques. The model is structurally composed of two cascaded encoder–decoder networks, each of which is constructed by four CNN layers and two full connection layers. The front model is built on backpropagation learning for segmenting a colonoscopic polyp image. The output images from the precedent hetero-encoder are regarded as corrupted labeled images, especially during the time period close to the end of learning, and are selectively fed into the successive auto-encoder for denoising learning to enhance its discriminative power and relieve the problem of a lack of labeled data for medical image tasks. The performance of the proposed model can be further improved by a simple fuzzy logic approach setting the regularization parameter in the loss function. The proposed method utilizes features learned from some open medical datasets and our own collected dataset. The performance of the proposed architecture is compared with a state-of-the-art network. The evaluation shows the performances of the proposed method are consistent across all the datasets and often outperform the state-of-art model.

Addressing priority challenges in the detection and assessment of colorectal polyps from capsule endoscopy and colonoscopy in colorectal cancer screening using machine learning

Background: Colorectal capsule endoscopy (CCE) is a potentially valuable patient-friendly technique for colorectal cancer screening in large populations. Before it can be widely applied, significant research priorities need to be addressed. We present two innovative data science algorithms which can considerably improve acquisition and analysis of relevant data on colorectal polyps obtained from capsule endoscopy.Material and methods: A fully paired study was performed (2015–2016), where 255 participants from the Danish national screening program had CCE, colonoscopy, and histopathology of all detected polyps. We developed: (1) a new algorithm to match CCE and colonoscopy polyps, based on objective measures of similarity between polyps, and (2) a deep convolutional neural network (CNN) for autonomous detection and localization of colorectal polyps in colon capsule endoscopy.Results and conclusion: Unlike previous matching methods, our matching algorithm is able to objectively quantify the similarity between CCE and colonoscopy polyps based on their size, morphology and location, and provides a one-to-one unequivocal match between CCE and colonoscopy polyps. Compared to previous methods, the autonomous detection algorithm showed unprecedented high accuracy (96.4%), sensitivity (97.1%) and specificity (93.3%), calculated in respect to the number of polyps detected by trained nurses and gastroenterologists after visualizing frame-by-frame the CCE videos.

Risk of delayed bleeding before and after implementation of cold snare polypectomy in a screening colonoscopy setting.

Background and study aims Cold snare polypectomy (CSP) is considered to be effective in reducing risk of delayed bleeding but randomized trials fail to support this owing to the small sample size. The current study aimed to compare risk of delayed bleeding before and after implementation of CSP in a screening colonoscopy setting. Patients and methods This study retrospectively analyzed a prospectively maintained screening colonoscopy database in a university hospital in Taiwan. We compared the rate of delayed bleeding before and after implementation within similar periods (18 months and 15 months) and the respective number of polypectomies (1,304 and 1,255) performed to remove small and diminutive polyps. The main outcome measurement was delayed bleeding within the two periods. Multivariate analysis was performed to adjust for major confounders. Results A total of 1,304 and 1,225 subjects received hot snare polypectomy (HSP) and CSP in two separate periods, respectively. Compared with the HSP, the CSP had a lower rate of delayed bleeding (0.1 % vs . 1.1 %, P < 0.001), severe bleeding (0 % vs. 0.7 %, P < 0.01), need for second-look colonoscopy (0 % vs. 0.8 %, P < 0.01), and emergency service visits (0.1 % vs . 1.0 %, P < 0.01). Total procedure time (12.60 ± 11.45 vs . 16.48 ± 14.27 min/person, P < 0.01) and duration of hospital stay (1.18 ± 0.50 vs . 1.53 ± 5.78 hour/person, P < 0.03) were also shorter after CSP implementation. Multivariate analysis showed that HSP was an independent risk factor for delayed bleeding after adjusting for age, gender, and number of polyps (adjusted odds ratio 14.4;95 % confidence interval = 1.88 – 110.6). Conclusion Implementation of CSP significantly reduces risk of delayed bleeding associated with removing small and diminutive polyps in screening colonoscopy.

Polyp detection with computer-aided diagnosis in white light colonoscopy: comparison of three different methods.

Background and study aims Detection of polyps during colonoscopy is essential for screening colorectal cancer and computer-aided-diagnosis (CAD) could be helpful for this objective. The goal of this study was to assess the efficacy of CAD in detection of polyps in video colonoscopy by using three methods we have proposed and applied for diagnosis of polyps in wireless capsule colonoscopy. Patients and methods Forty-two patients were included in the study, each one bearing one polyp. A dataset was generated with a total of 1680 polyp instances and 1360 frames of normal mucosa. We used three methods, that are all binary classifiers, labelling a frame as either containing a polyp or not. Two of the methods (Methods 1 and 2) are threshold-based and address the problem of polyp detection (i. e. separation between normal mucosa frames and polyp frames) and the problem of polyp localization (i. e. the ability to locate the polyp in a frame). The third method (Method 3) belongs to the class of machine learning methods and only addresses the polyp detection problem. The mathematical techniques underlying these three methods rely on appropriate fusion of information about the shape, color and texture content of the objects presented in the medical images. Results Regarding polyp localization, the best method is Method 1 with a sensitivity of 71.8 %. Comparing the performance of the three methods in the detection of polyps, independently of the precision in the location of the lesions, Method 3 stands out, achieving a sensitivity of 99.7 %, an accuracy of 91.1 %, and a specificity of 84.9 %. Conclusion CAD, using the three studied methods, showed good accuracy in the detection of polyps with white light colonoscopy.

Screening Colonoscopy Polyp, Adenoma and Sessile Serrated Adenoma Detection Rate Differences in Hispanics and Whites in Age-Matched Cohorts

Introduction: Colorectal cancer is the third leading cause of cancer death in Hispanics. Hispanics are a rapidly growing population within the United States. Although Whites appear to have higher rates of colorectal cancer compared to Hispanics, data may be flawed by differences in access to care. Our objective was to compare polyp, adenoma and sessile serrated adenoma prevalence among age-matched Hispanic and White cohorts. Methods: Colonoscopy quality data was collected prospectively at our single tertiary referral center from June 2012 to June 2018 using Qualoscopy (Docbot, Inc.). Among screening colonoscopies we compared Hispanics to Whites in age-matched cohorts for polyp (PDR), adenoma (ADR) and sessile serrated adenoma detection rates (SSADR). Subgroup analysis was performed on left vs. right colon polyps. Significance was determined by a two-tailed Fischer’s exact test. Results: 3097 colonoscopies met our inclusion criteria, of which 463 were performed in Hispanics and 2634 in Whites. Baseline characteristics are shown in Table 1. No significant difference in PDR, ADR and SSADR was seen before age 40 or after age 60. However, Hispanics aged 40-49 had a statistically significant lower PDR compared to Whites within the entire colon, 0.44 vs. 0.67 and within the left colon, 0.26 vs. 0.48, respectively. Hispanics aged 50-59 had statistically lower PDR, ADR and SSADR compared to Whites, 0.50 vs. 0.69, 0.34 vs. 0.44 and 0.05 vs. 0.11, respectively. Hispanics aged 50-59 had significantly lower PDR in the left colon 0.33 vs. 0.47, significantly lower PDR in the right colon 0.36 vs. 0.48 and significantly lower ADR in the right colon 0.25 vs. 0.32, respectively. Interestingly, PDR, ADR and SSADR was only marginally higher between Hispanics aged 40-49 vs. Hispanics aged 50-59 and Whites aged 40-49 vs. Whites aged 50-59. Conclusion: Our data demonstrate Hispanics have statistically significant lower PDR in ages 40-49 and 50-59 and lower ADR and SSADR in ages 50-59 compared to Whites. We also know that sessile serrated adenomas are thought to play a role in the development of interval colorectal cancer. Lower PDR, ADR and especially SSADR in Hispanics aged 50-59 may play a pivotal role in the lower rates of colorectal cancer seen in Hispanics.115_A Figure 1. Baseline Characteristics115_B Figure 2. Screening Colonoscopy Polyp, Adenoma and Sessile Serrated Adenoma Detection Rates in Hispanics and Whites115_C Figure 3. Screening Colonoscopy Polyp, Adenoma and Sessile Serrated Adenoma Detection Rates in Hispanics and Whites Based on Colon Location in Ages 40-49 and 50-59

Risk Analysis of Colorectal Post-Polypectomy Bleeding Due to Antithrombotic Agent

Background/Aims: Post-polypectomy bleeding (PPB) is a major complication of colorectal polypectomy, and antithrombotics is one of the major risk factors of PPB. The purpose of this study was to investigate PPB risks with regard to the combinations of antithrombotic agents used. Methods: We retrospectively reviewed cases involving colonoscopic polyp resection between September 2002 and December 2014. The risk of PPB was assessed according to patient and lesion factors, including antithrombotic use. Antithrombotics were discontinued before polypectomy. Results: A total of 6,382 colonoscopies with 12,876 polypectomies were analyzed. PPB occurred in 55 patients (0.9%) and 63 lesions (0.5%). Among patients treated with antithrombotics, heparin bridging (HB) therapy was an independent risk factor of PPB (per patient, 20%, OR 33.1, p < 0.001; per lesion, 9.1%, OR 17.3, p < 0.001) compared to those without antithrombotics (per patient 0.7%; per lesion 0.4%). Among patients without HB, the combination of anticoagulant + antiplatelet agents was significantly associated with PPB (per patient, 5%, OR 7.73, p = 0.007; per lesion, 2.4%, OR 6.31, p = 0.003). Conclusion: HB therapy is a major risk factor for PPB. Among patients without HB, anticoagulant + antiplatelet therapy was a significant risk factor for PPB.

G-EYE advanced colonoscopy for improved polyp detection rates - a randomized tandem pilot study with different endoscopists.

The most commonly missed polyps incolonoscopy are those located behind haustral folds. The G-EYE system is a standard colonoscope consisting of re-processable balloon at its distal tip. The G-EYE balloon improves the detection of polyps by straightening the haustral folds. In our back-to-back tandem study, we aimed to determine whether and to what extent the G-EYE system could reduce adenoma miss rates in screening colonoscopy. Patients referred to colonoscopy were randomized into 2 groups. Group A underwent a standard colonoscopy (SC) followed by balloon colonoscopy (BC), and Group B underwent BC followed by SC. In this randomized tandem study, the investigator's level of training and the endoscopists themselves were changed after each withdrawal. Each endoscopist was blinded to the results of the first withdrawal. Fifty-eight patients were enrolled and randomized into 2 groups with similar baseline characteristics. Nine patients were excluded from the study. Twenty-five patients underwent SC followed by BC while 24 underwent BC followed by SC. The adenoma miss rate for SC was 41 %, with an additional detection rate of 69 % for BC (ratio 1.69). The overall miss rate for polyps was 60 % for SC, with an additional detection rate of 150 % for BC (ratio 2.5). Experienced investigators who used BC were able to identify an additional 7 polyps while inexperienced investigators. Although our results could not clearly confirm that BC improves adenoma detection, the investigator's experience appears to be a major determinant of the adenoma detection rate.

Genetic profile of polyps and risk of advanced metachronous lesions.

555 Background: The role of genetic profile of polyps to predict advanced metachronous lesions (AML) remains unknown. The aim is to study the relation between genetic profile of polyps and both risk of AMLs and time to develop them in surveillance. Methods: 308 patients with colonic polyps were consecutively enrolled between 2007 and 2009 for this cohort study, and followed up to 2014 (median 26 months, range 63). Variables as age, sex, smoking, weight, number of colonoscopies and number and characteristics of polyps were collected. 995 polyps were analyzed for somatic mutations on BRAF and KRAS genes using allelic discrimination by real-time PCR and direct DNA sequenciation, respectively. High level of methylation on CpG islands (CIMP-H) was also tested using MS-MLPA. AML was defined by a size higher than 9mm, high grade dysplasia or villous component. Risk of developing AML for individual genetic markers was studied using Chi-square tests and logistic regression. Log-rank test with Kaplan Meier survival curves and Cox-regression model were also performed. Multivariate analysis were adjusted by sex, age, familial colorectal cancer, smoking and features of AML in first colonoscopy. Results: 21% of polyps in first colonoscopy were CIMP-H. KRAS and BRAF mutations accounted for 25% and 17% of polyps, respectively. In univariate analysis, KRAS-mutated polyps were related to higher risk of AML in surveillance (52% KRAS-mutated polyps vs 31% non-mutated; p = 0.01). Similar results were obtained regarding CIMP-H (77% CIMP-H polyps vs 38% non-CIMP; p = 0.005). Logistic regression showed CIMP-H as the unique genetic marker of risk for AML (OR 11.41, 95% CI 2.04-63.70; p = 0.006). Regarding time to develop AML, shorter intervals were found related to CIMP-H (median of 31 vs 48 months in non-CIMP-H; p = 0.002) and KRAS-mutations (median of 36 vs 49 months in non-mutated; p = 0.029) in univariate analysis. Multivariate analysis highlighted CIMP-H as the unique independent marker associated to shorter time to develop AML (HR 4.01, 95% CI 1.36-10.46; p = 0.01). Conclusions: Presence of CIMP-H in polyps associates higher risk of subsequent AML and shorter interval to their development. Genetic profile of polyps emerges as useful tool for colonoscopy surveillance.

Combined Cap-Assisted Total Water With Chromoendoscopy Further Enhance Proximal Adenoma Detection (ADR) and Hyperplastic Polyp Detection: A Retrospective Analysis

Introduction: Missed lesions in proximal colon contribute to interval cancers. Water exchange (WE) combined with chromoendoscopy increased ADR (JIG2012;3:114). Cap-assisted WE further increased ADR (GIE2013;77:944). Combined use of cap-assisted total water colonoscopy, eliminating air, further increased proximal ADR in screening cases. We hypothesize that combined cap-assisted total water with chromoendoscopy on scope withdrawal can further improve proximal ADR in surveillance colonoscopy.Table: Table. Patients demographics, volume of water used, cecal intubation and bowel preparation scoreTable: Table. Adenomas and hyperplastic polyps detection in proximal colonMethods: Retrospective analysis of 3 consecutive series of patients examined with cap-assisted water exchange (CAWE), cap-assisted total water (CATW) and combined cap-assisted total water and chromoendoscopy (CATWC) (with 0.002% indigocarmine/water). CAWE was performed with air turned off and water was infused to facilitate scope insertion while dirty water was suctioned on insertion and withdrawal. Air was used on withdrawal to facilitate examination/removal of lesions. Insertion method was same as CAWE for CATW and CATWC. In CATW, plain water was used and exchanged, with air pockets suctioned to facilitate examination. In CATWC, indigocarmine solution was infused upon withdrawal from cecum and dirty water was exchanged. In both groups, no air was used for entire examination, and polypectomy was done underwater. Small (<5 mm) polyps were removed with biopsy forceps; 5-8 mm polyps, cold snare; and >8 mm polyps, hot snare. Results: 105 patients (35 per group) were included. Patients' demographics were comparable, with no difference in mean interval between index screening and surveillance colonoscopy (4; 4.12; 4.14 years respectively). Total amount of water infused and suctioned were comparable between CATW and CATWC but significantly more than CAWE, and so was the withdrawal time. The overall and proximal ADRs (< 5mm) were higher for CATWC compared with CATW and CAWE (P<0.05). The proximal hyperplastic polyp detection rate was significantly higher for CATWC when compared to CATW and CAWE (40% vs.14.3% vs.14.3% respectively, P<0.05). Conclusion: Limitations: retrospective analysis of consecutive series with small number of patients. Combined cap-assisted total water and chromoendoscopy (CATWC) further improved proximal ADR especially <5mm adenomas. It significantly increased detection of proximal hyperplastic polyps (closely related to sessile serrated polyps) (CGH2013;11:760) in surveillance colonoscopy. These intriguing preliminary data deserves to be confirmed in a prospective RCT.

Clinical application of simethicone emulsion on bowel preparation for colonoscopy

Objective To assess the clinical effects of simethicone emulsion combined with polyethylene glycol on bowel preparation for colonoscopy. Methods Two hundred out-patients, who underwent colonoscopy, were randomly divided into the study group and the control group. The study group was given simethicone in addition with polyethylene glycol, and the control group was given polyethylene glycol only. The differences on bowel preparation scores, air bubble reduction rate, colon lens sharpness, ileocecal region arrival time, colon polyp detection rate, the number of colon poly detection, and adverse event rate between the two groups were compared. Results The air bubble reduction rate, colon lens sharpness score and ileocecal region arrival time of the study group was 1(0-3) score, 1.0(0-2) score, and 9 (5-21) min, respectively, which was 2 (1-3) score, 1.5 (0-2) score and 12 (6-22) min, respectively in the control group. Differences between the two groups were statistically significant(Z=-9.490, P=0.000; Z=-6.768, P=0.000; Z=-5.521, P=0.000). For the bowel preparation score, colonoscopy polyp detection rate, the detection rate of colon polyp of diameter less than 5 mm, and number of colonoscopy polyp detection, there was no statistical difference between the two groups (P>0.05). No adverse events were observed in the both two groups. Conclusion The bowel preparation using simethicone combined with polyethylene glycol could effectively decrease the number of air bubble, enhance colon lens sharpness and shorten operation time, which contributes significant improvement for colonoscopy quality. Key words: Colonoscopy; Bowel preparation; Simethicone; Polyethylene glycol

Efficacy and safety of cold snare resection in preventive screening colonoscopy.

Background and aim Removal of polyps during colonoscopy effectively prevents the development of colorectal cancer. So far, snare resection with high frequency current with or without prior submucosal saline injection is the method of choice. The aim of this study was to evaluate the feasibility, safety, and outcome of cold snare resection during routine endoscopy. Methods In this prospective study, 522 patients undergoing outpatient colonoscopy were included. Cold snare resection for diminutive (< 6 mm), small (6 – 9 mm), and larger polyps (> 9 – 15 mm) was performed using a dedicated cold snare device (Exacto ® ) without prior submucosal injection. Outcome parameters included bleeding rate, perforation rate, procedure time, histologic evaluation of polyp margins, and success rates. The data were compared to a group of patients undergoing hot snare resection. Results Overall, 1233 polyps were removed using cold snare resection with an overall success rate of 99.4 %. All failures of cold snare resection occurred in the cecum (8/82, failure rate 9.8 %). In the remaining colon, the success rate was 100 %. Immediate post-polypectomy bleeding occurred in 0.49 % of all patients and was most frequently seen in polyps larger than 9 mm. The procedure time was significantly shorter using cold snare resection compared with hot snare resection (27.6 min vs. 35.7 min, P < 0.01). Conclusion Cold snare resection can be performed safely in outpatients for removal of small polyps in screening colonoscopy. It does not require prior saline injection and reduces procedure time without an increased risk of bleeding.