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Objectives: There have been significant advances in the management of large (≥20 mm) laterally spreading tumors (LSTs) or nonpedunculated colorectal polyps; however, there is a lack of clear consensus on the management of these lesions with significant geographic variability especially between Eastern and Western paradigms. We aimed to provide an international consensus to better guide management and attempt to homogenize practices., Methods: Two experts in interventional endoscopy spearheaded an evidence-based Delphi study on behalf of the World Endoscopy Organization Colorectal Cancer Screening Committee. A steering committee comprising six members devised 51 statements, and 43 experts from 18 countries on six continents participated in a three-round voting process. The Grading of Recommendations, Assessment, Development and Evaluations tool was used to assess evidence quality and recommendation strength. Consensus was defined as ≥80% agreement (strongly agree or agree) on a 5-point Likert scale., Results: Forty-two statements reached consensus after three rounds of voting. Recommendations included: three statements on training and competency; 10 statements on preresection evaluation, including optical diagnosis, classification, and staging of LSTs; 14 statements on endoscopic resection indications and technique, including statements on en bloc and piecemeal resection decision-making; seven statements on postresection evaluation; and eight statements on postresection care., Conclusions: An international expert consensus based on the current available evidence has been developed to guide the evaluation, resection, and follow-up of LSTs. This may provide guiding principles for the global management of these lesions and standardize current practices., (© 2024 The Authors. Digestive Endoscopy published by John Wiley & Sons Australia, Ltd on behalf of Japan Gastroenterological Endoscopy Society.)

The incidence and mortality of colorectal cancer (CRC) have decreased through regular screening colonoscopy, surveillance, and endoscopic treatment. However, CRC can still be diagnosed after negative colonoscopy. Such CRC is called interval CRC and accounts for 1.8-9.0% of all CRC cases. Most cases of interval CRC originate from missed lesions and incompletely resected lesions. Interval CRC can be minimized by improving the quality of colonoscopy. This has led to a growing interest in and demand for high-quality colonoscopy. It is important to reduce the risk of CRC and its associated mortality by improving the quality of colonoscopy. In this review article, we provide an overview of colonoscopy quality indicators, including bowel preparation adequacy, the cecal intubation rate, the adenoma detection rate, the colonoscopy withdrawal time, appropriate polypectomy, and complication of the procedure. Because colonoscopy is a highly endoscopist-dependent procedure, colonoscopists should be well-acquainted with quality indicators and strive to apply them in daily clinical practice for the prevention of CRC.

Background: This study aimed to determine short-term and long-term outcomes according to time intervals after stenting and compared them with those of emergency surgery (ES) in colorectal cancer (CRC) with malignant obstruction., Methods: CRC with malignant obstructions was reviewed retrospectively between January 2008 and July 2018. Of a total of 539 patients who visited the emergency room and underwent ES, 133 were enrolled in the ES group. Of a total of 567 patients who initially received stenting and subsequently underwent elective surgery, 220 were enrolled in the SEMS group. The interval between SEMS placement and elective surgery was classified as < 11 days, 11-17 days, and > 17 days., Results: For those who received SEMS (n = 220), those with a time interval of 11-17 days (n = 97) had fewer hospital days than those with a time interval of < 11 days (n = 68) (8 days vs. 15 days) and less stoma formation than those with a time interval of > 17 days (n = 55) (1.0% vs. 14.6%). Multivariable analysis revealed a decreased risk of death for the group with a time interval of 11-17 days (20.6%) compared to the ES group (31.6%) (hazard ratio: 0.48; 95% confidence interval: 0.24-0.97). Disease-free survival was comparable between the SEMS and ES groups regardless of the time interval (log-rank p = 0.52)., Conclusions: The time interval of 11-17 days after stenting to elective surgery appeared to be associated with the most favorable outcomes., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Background: Endoscopic submucosal dissection (ESD) can provide a high en bloc resection rate and has been widely applied as curative treatment for early colorectal cancer (ECC). However, surgical treatment is occasionally required, and reports on the long-term prognosis of ESD are insufficient. This study aimed to investigate the long-term outcomes of ECC removal by ESD, including local recurrence and metastasis., Methods: This multicenter study was conducted retrospectively on 450 consecutive patients with ECC who were treated with ESD between November 2003 and December 2013. Clinical, pathological, and endoscopic data were collected to determine tumor depth, resection margin, lymphovascular invasion, and recurrence., Results: The median follow-up period was 53.8 (12-138 months). The en bloc resection rate was 85.3% (384) and in intramucosal cancer being 84.1% and in superficial submucosal invasion (SM1) cancer being 89.8% (p = 0.158). The curative resection rate was 76.0% (n = 342), and there was no statistical difference between the two groups (77.3% vs. 71.4%, p = 0.231). The overall recurrence free survival rate (RFS) was 98.7% (444/450). In patients with curative resection, there was no statistically significant difference in RFS according to invasion depth (intramucosal: 99.3% vs. SM1: 97.1%, p = 0.248)., Conclusions: Patients with curatively resected ECC treated with ESD showed favorable long-term outcomes. Curatively resected SM1 cancer has a RFS similar to that of intramucosal cancer., (© 2022. The Author(s).)

Background: When endoscopically resected specimens of early colorectal cancer (CRC) show high-risk features, surgery should be performed based on current guidelines because of the high-risk of lymph node metastasis (LNM). The aim of this study was to determine the utility of an artificial intelligence (AI) with deep learning (DL) of hematoxylin and eosin (H&E)-stained endoscopic resection specimens without manual-pixel-level annotation for predicting LNM in T1 CRC. In addition, we assessed AI performance for patients with only submucosal (SM) invasion depth of 1000 to 2000 μm known to be difficult to predict LNM in clinical practice., Methods: H&E-stained whole slide images (WSIs) were scanned for endoscopic resection specimens of 400 patients who underwent endoscopic treatment for newly diagnosed T1 CRC with additional surgery. The area under the curve (AUC) of the receiver operating characteristic curve was used to determine the accuracy of AI for predicting LNM with a fivefold cross-validation in the training set and in a held-out test set., Results: We developed an AI model using a two-step attention-based DL approach without clinical features (AUC, 0.764). Incorporating clinical features into the model did not improve its prediction accuracy for LNM. Our model reduced unnecessary additional surgery by 15.1% more than using the current guidelines (67.4% vs. 82.5%). In patients with SM invasion depth of 1000 to 2000 μm, the AI avoided 16.1% of unnecessary additional surgery than using the JSCCR guidelines., Conclusions: Our study is the first to show that AI trained with DL of H&E-stained WSIs has the potential to predict LNM in T1 CRC using only endoscopically resected specimens with conventional histologic risk factors., (© 2022. Japanese Society of Gastroenterology.)

Background: An association between Helicobacter pylori infection and colorectal neoplasia has been reported in cross-sectional studies., Goals: We examined the association between H. pylori infection and the development of advanced colorectal neoplasia (AN) in a screening cohort., Study: We identified 3753 adults, who underwent screening and subsequent surveillance colonoscopies. The primary outcome was the development of metachronous AN, as confirmed by surveillance colonoscopy. H. pylori infection status was assessed by an H. pylori-specific immunoglobulin G antibody test. Sensitivity analysis was also performed by H. pylori infection status on the basis of histology., Results: During a median follow-up of 41 months, the incidence of AN was 3.2% and 1.7% in participants with and without H. pylori infection, respectively. In multivariable analysis adjusted for age, body mass index, smoking status, alcohol intake, family history of colorectal cancer, and baseline adenoma characteristics, the hazard ratio [95% confidence interval (CI)] for metachronous AN was 1.74 (1.11-2.73) in participants with H. pylori seropositivity, compared with those without H. pylori seropositivity. The association was consistent with H. pylori infection status on the basis of histology (adjusted hazard ratio, 3.51; 95% CI, 1.64-7.51). In the subgroup analysis, the positive association was observed in both no-adenoma and adenoma removal subgroups., Conclusions: In a cohort study, H. pylori infection was associated with an increased risk of AN development. This association was consistent in both the serological and histologic assessment of H. pylori infection. Prospective studies are necessary to determine whether H. pylori eradication can reduce the risk of colorectal neoplasia.

Although colorectal cancer (CRC) is considered one of the most preventable cancers, no non-invasive, accurate diagnostic tool to screen CRC exists. We explored the potential of urine nuclear magnetic resonance (NMR) metabolomics as a diagnostic tool for early detection of CRC, focusing on advanced adenoma and stage 0 CRC. Urine metabolomics profiles from patients with colorectal neoplasia (CRN; 36 advanced adenomas and 56 CRCs at various stages, n = 92) and healthy controls (normal, n = 156) were analyzed by NMR spectroscopy. Healthy and CRN groups were statistically discriminated using orthogonal projections to latent structure discriminant analysis (OPLS-DA). The class prediction model was validated by three-fold cross-validation. The advanced adenoma and stage 0 CRC were grouped together as pre-invasive CRN. The OPLS-DA score plot showed statistically significant discrimination between pre-invasive CRN as well as advanced CRC and healthy controls with a Q2 value of 0.746. In the prediction validation study, the sensitivity and specificity for diagnosing pre-invasive CRN were 96.2% and 95%, respectively. The grades predicted by the OPLS-DA model showed that the areas under the curve were 0.823 for taurine, 0.783 for alanine, and 0.842 for 3-aminoisobutyrate. In multiple receiver operating characteristics curve analyses, taurine, alanine, and 3-aminoisobutyrate were good discriminators for CRC patients. NMR-based urine metabolomics profiles significantly and accurately discriminate patients with pre-invasive CRN as well as advanced CRC from healthy individuals. Urine-NMR metabolomics has potential as a screening tool for accurate diagnosis of pre-invasive CRN.

Background and Aim: Sarcopenia is a pathological condition characterized by the progressive loss of muscle mass and increased amount of visceral fat. Recent evidence has revealed that sarcopenia is associated with certain diseases. However, the impact of sarcopenia on colorectal neoplasia has not been documented clearly. We studied the association between sarcopenia and advanced colorectal neoplasia in a large screening population., Methods: This cross-sectional study included 14 024 asymptomatic adults who underwent first-time screening colonoscopy. Sarcopenia (class II) was defined as an appendicular skeletal muscle mass (ASM)/bodyweight (%) value more than two standard deviations below the mean for healthy young adults. ASM was estimated using bioelectrical impedance analysis., Results: In a multivariable model adjusted for age, sex, obesity (body mass index ≥ 25), smoking status, alcohol intake, regular exercise, and family history of colorectal cancer, the odds ratio (OR) for advanced colorectal neoplasia on comparing participants with sarcopenia (class II) to those without sarcopenia (class I + II) was 1.52 (95% confidence interval [CI], 1.23-1.86). Further adjustment for metabolic parameters attenuated this association, but the association was still significant (OR, 1.34; 95% CI, 1.07-1.68). Furthermore, the multivariable (traditional risk factors)-adjusted OR associated with a 1% decrease on the introduction of ASM/weight% as a continuous variable in regression models was 1.04 (95% CI, 1.01-1.07) for advanced colorectal neoplasia., Conclusions: Our findings indicate that sarcopenia is significantly and progressively associated with the risk of advanced colorectal neoplasia. This association might be explained by metabolic factors that could be potential mediators of the effect of sarcopenia., (© 2018 Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.)

Objectives: Individuals with advanced adenomas or three or more adenomas have a higher risk of metachronous advanced neoplasia (AN) and are recommended to undergo surveillance colonoscopy at shorter intervals. However, it is questionable whether patients with multiple (three or more) non-advanced diminutive adenomas should be considered as high-risk., Methods: We analyzed 5482 patients diagnosed with one or more adenomas during their first colonoscopy screening and who underwent a follow-up colonoscopy. Patients were categorized into four groups based on adenoma characteristics at baseline: Group 1, 1-2 non-advanced adenomas; Group 2, ≥3 non-advanced, diminutive (1 to 5 mm) adenomas; Group 3, ≥3 non-advanced, small (6-9 mm) adenomas; and Group 4, advanced adenomas., Results: During a median follow-up of 38 months, the incidence of metachronous AN at surveillance colonoscopy was 5.6%. The incidence of AN was 3.9% in group 1, 5.9% in group 2, 10.6% in group 3, and 22.1% in group 4. The adjusted hazard ratios (HRs) [95% confidence intervals (CIs)] for metachronous AN between group 2, group 3, and group 4, and low risk group 1 were 1.71 (0.99-2.94), 2.76 (1.72-4.44), and 5.23 (3.57-7.68), respectively. Compared with group 4, the adjusted HRs (95% CIs) for group 1, group 2, and group 3 were 0.19 (0.13-0.28), 0.32 (0.18-0.59), and 0.52 (0.31-0.89), respectively., Conclusions: We found that patients with three or more non-advanced diminutive adenomas had a borderline increased risk of metachronous AN compared with patients with low risk adenomas.

Background and Aims: In individuals with either no or 1 to 2 nonadvanced adenomas, future risks of advanced colorectal neoplasia (AN) vary according to clinical risk factors. However, little is known about the association between the adenoma detection rate (ADR) and the risk for metachronous AN in patients with low-risk adenomas., Methods: We identified 7171 participants with no or 1 to 2 nonadvanced adenomas at first-time screening colonoscopy. The risk of metachronous AN was investigated at surveillance colonoscopy, according to clinical characteristics and the ADR., Results: In multivariate analysis the risk for metachronous AN was strongly associated with increasing age, male sex, increasing number of adenomas, and the ADR of the endoscopist. With the ADR modeled as a continuous variable, each 1.0% increase in the rate of ADR predicted a 3.0% decrease in the risk of metachronous AN (adjusted odds ratio [OR], .97; 95% confidence interval [CI], .95-.99). With the ADR modeled using a binary cut-off (32%), the risk of metachronous AN was reduced in patients of endoscopists with an ADR ≥32% (adjusted OR, .53; 95% CI, .35-.83). Moreover, the risk of metachronous AN was reduced (adjusted OR, .66; 95% CI, .46-.95) in patients of endoscopists with an ADR in the highest tertile, compared with patients of endoscopists with ADRs in the lowest tertile. The impact of ADR on metachronous AN was significant for patients with low-risk adenomas rather than patients with no adenoma., Conclusions: In patients with low-risk adenomas, the ADR of the endoscopist was inversely associated with the risk of metachronous AN., (Copyright © 2018 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.)

Obesity is a well-known risk factor for colorectal neoplasia. Yet, the associations of both metabolic and obesity status with metachronous colorectal neoplasia remain unclear. We conducted a cohort study of 9,331 adults who underwent screening colonoscopy and surveillance colonoscopy. Participants were classified as metabolically healthy if they had no metabolic syndrome component. Participants were categorized into four groups according to body mass index and metabolic status: metabolically healthy non-obese (MHNO; n = 2,745), metabolically abnormal non-obese (MANO; n = 3,267), metabolically healthy obese (MHO; n = 707), and metabolically abnormal obese (MAO; n = 2,612). MAO individuals [n = 159 advanced colorectal neoplasia (AN) cases, 6.1%] and MANO individuals (n = 167 AN cases, 5.1%) had a higher incidence of AN compared with MHNO individuals (n = 79 AN cases, 2.9%). In a multivariable model, the risk of metachronous AN was higher in MANO (hazard ratio [HR] 1.43, 95% confidence interval [CI] 1.12-1.84) and MAO (HR 1.52, 95% CI 1.18-1.96) than in MHNO. In contrast, the risk of metachronous AN was not significantly elevated in MHO. In subgroup analyses, with or without adenoma at baseline, MAO was a risk group for metachronous AN, and MHO was not. Our findings suggest that metabolic unhealthiness is a significant predictor for metachronous AN.

Background: The role of Helicobacter pylori (H. pylori) in the development of colorectal neoplasm remains controversial. We examined the association between H. pylori infection and colorectal neoplasm in a large sample of healthy participants who underwent screening colonoscopy., Methods: A cross-sectional study of 8916 men, who participated in a regular health-screening examination that included an H. pylori-specific immunoglobulin G antibody test and colonoscopy, was conducted to evaluate the association between H. pylori and colorectal neoplasm., Results: Multivariable analyses adjusted for age, body mass index, smoking status, alcohol intake, regular exercise, regular aspirin use, and family history of colorectal cancer showed that the odds ratio (OR) (95% confidence interval [CI]) for any adenoma and advanced neoplasm was 1.32 (1.07-1.61) and 1.90 (1.05-3.56) in participants with H. pylori infection and without H. pylori infection, respectively. The association persisted after further adjustment for inflammatory markers or metabolic variables including fasting blood glucose, triglycerides, high-density lipoprotein-cholesterol, and low-density lipoprotein-cholesterol. Regarding the location, a positive association was confined to cases with proximal adenomas and was observed similarly in all the evaluated subgroups., Conclusions: In a large-scale study, carefully controlled for confounding factors, involving asymptomatic participants without a history of colonoscopy, H. pylori infection was significantly associated with the risk of any colorectal adenoma and advanced colorectal neoplasm. Prospective studies are necessary to determine whether H. pylori eradication can reduce this risk., (© 2017 John Wiley & Sons Ltd.)

The prognosis of early-onset sporadic colorectal cancer (CRC) patients remains controversial. The objective of this study was to assess the long-term outcome and prognostic factors of sporadic CRC in young patients.From 2006 to 2011, 8207 patients underwent curative or palliative surgery for CRCs in our institution. A total of 693 patients who were ≤45 years old with sporadic CRC were enrolled as the young group. A total of 1823 patients aged between 56 and 65 years were identified as middle-aged control group for this study. Survival outcome and prognostic factors were compared between the two groups.Young patients had higher recurrence rate than older patients in stages I and II (8.8% vs 2.7%, P <0.001). There was no significant difference of recurrence rate in stage III and IV cancers (27.5% vs 27.9%, P = 0.325). Metachronous cancers were developed more frequently in young patients (1.4% vs 0.6%, P = 0.038). Advanced stage CRC was diagnosed significantly more common in the young group (55.6% vs 47.9%, P = 0.001). High microsatellite instability (MSI) tumors are less likely to have advanced stage cancers (odds ratio (OR) 0.23, 95% confidence interval (CI) = 0.07-0.70) or cancer recurrence (OR 0.11, 95% CI = 0.01-0.85) in young patients. Cancer-specific survival was worse in young patients than that in older patients (81.2% vs 87.8%, P <0.001). However, there was no significant difference in cancer-specific survival for each stage between the two groups. Independent prognostic factors for survival in young patients were undifferentiated cancer (hazard ratio (HR) 2.30, 95% CI = 1.23-4.31) and 3 months or longer duration of symptom (HR 2.57, 95% CI = 1.34-4.94). Young women had better survival compared with young men (HR 0.55, 95% CI = 0.33-0.90).Prognosis of sporadic CRC in young patients is poorer than older patients, because of poorer histologic differentiation and delay in diagnosis. Early detection of CRC confers survival benefit to young patients. Because of higher recurrence rate and metachronous cancer risk, post-operative surveillance is also important in young patients.

Background: Genome-wide methylation arrays have revealed aberrant methylation of N-Myc downstream-regulated gene 2 (NDRG2) promoter in colorectal cancer (CRC). This study investigated the role of NDRG2 in colorectal carcinogenesis., Methods: The aberrant promoter methylation, mRNA, and protein expression of NDRG2 were evaluated in 27 pairs of human CRC and adjacent normal tissues and seven human CRC-derived cell-lines. After stable NDRG2 over-expressed RKO and DLD-1 human CRC cell-lines were constructed, in vitro functional assays, including colony formation, cell viability, proliferation, invasion and migration assays, and in vivo xenograft models were performed., Results: The promoter of NDRG2 was methylated in 89% human CRC tissue compared to adjacent normal colonic mucosa (7.4%; P < 0.001). High-level methylation of NDRG2 promoter was more prevalent in proximal CRC (P = 0.022) and advanced T stage (P = 0.039). NDRG2 mRNA and protein expression was down-regulated in 89% and 100% human CRC tissue, respectively. In human CRC cell-lines, the promoter of NDRG2 was methylated aberrantly and mRNA, and protein expression of NDRG2 was down-regulated. NDRG2 mRNA expression was reactivated by 5-aza-2'-deoxycytidine. Colony formation of NDRG2 over-expressing RKO cells was inhibited (P = 0.012), as was the viability, proliferation, and invasion of NDRG2 over-expressing DLD-1 cells (P < 0.001, P = 0.003, and P = 0.044, respectively). Tumor volume in xenograft mice transplanted with NDRG2 over-expressing RKO and DLD-1 cells was smaller than that in controls (P = 0.002 and P = 0.001, respectively)., Conclusions: Epigenetic silencing of NDRG2 induces proliferation and invasion of CRC and may be associated with proximal CRC and advanced T stage. NDRG2 methylation might serve as novel biomarker of CRC., (© 2015 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.)

Background/aims: An association between serum uric acid and cancer risk has been noted over the past few decades. There is ongoing debate about whether hyperuricemia represents an independent risk factor for colorectal neoplasm. We investigated the association between serum uric acid and prevalence of colorectal adenoma considering numerous confounding factors., Methods: A cross-sectional study was performed with individuals who underwent a routine health check-up examination, including a screening colonoscopy and blood chemistry. The association between serum uric acid and prevalence of colorectal adenoma was estimated from the results of a logistic regression analysis., Results: Of the 1,066 participants, 402 had colorectal adenoma (37.7%). In univariate models, the prevalence of colorectal adenoma was higher in participants in the fourth quartile uric acid level, compared to those in the first quartile uric acid level (OR, 1.67; 95% CI, 1.17-2.42; p=0.004). However, no significant association was detected between serum uric acid and prevalence of colorectal adenoma in multiple logistic regression analysis. A number of metabolic syndrome components exhibited a strong association with the prevalence of colorectal adenoma in the multivariate model (OR, 3.46 for highest vs. lowest; 95% CI, 1.30-9.20; p=0.021). Moreover, serum uric acid was strongly associated with metabolic syndrome-associated variables, including waist circumference, fasting blood glucose, systolic blood pressure, diastolic blood pressure, triglyceride, and high-density lipoprotein., Conclusions: Uric acid is not an independent risk factor for colorectal adenoma but is a risk indicator for metabolic syndrome-related colorectal adenoma.

Patients with inflammatory bowel disease (IBD) are at increased risk for developing colorectal cancer (CRC), although the overall incidence of IBD-associated CRC has been diminishing in recent decades in western countries. As demonstrated in previous studies, the risk of CRC in IBD increases with longer duration, extent of colitis, a familial history of CRC, coexistent primary sclerosing cholangitis, and the degree of inflammation. The pathogenesis of CRC in IBD is poorly understood. Similar to sporadic CRC, IBD-associated CRC is a consequence of sequential episodes of genomic alteration. Multiple inter-related pathways, including immune response by mucosal inflammatory mediators, oxidative stress, and intestinal microbiota, are also involved the pathogenesis of IBD-associated CRC. Continuing colonic inflammation appears to be a factor in the development of CRC; therefore, anti-inflammatory agents such as 5-aminosalicylate compounds and immune modulators have been considered as potential chemopreventive agents. Colonoscopic surveillance is widely accepted as being effective in reducing the risk of IBD-associated CRC, although no clear evidence has confirmed that surveillance colonoscopy prolongs survival in patients with extensive colitis. The traditional recommendation has been quadrantic random biopsies throughout the entire colon; however, several guidelines now have endorsed chromoendoscopy with a target biopsy because of increasing diagnostic yields and reduced workloads for endoscopists and pathologists. New technologies such as narrow band imaging, confocal endomicroscopy, and autofluorescence imaging have not yet been confirmed as surveillance strategies in IBD.

The aim of this study was to determine the correlation between microsatellite instability (MSI) and young age in patients with advanced colorectal adenomas. We retrospectively analyzed young patients (≤ 40 years of age) with advanced adenomas (n=84) between January 1996 and December 2006. We randomly selected the control group as patients ≥ 50 years of age with advanced adenomas (n=84) during the same time period. Of these patients, the MSI test and MLH1 immunohistochemistry were performed in the available tissue samples from patients with advanced adenomas. The number of patients who had the two tests was 52 in the young group and 49 in the old group. The monomorphic nature of the BAT26 panel for MSI analysis was used without comparison of normal tissue. MSI was detected in three young patients (n=52) and none of the old patients (n=49). There was no statistical difference between the two groups (P=0.243). All three young patients with MSI had a strong family history of colorectal cancer. MSI analysis was not a useful method of screening for HNPCC in young patients with advanced colorectal adenoma, at least in cases without a family history of colorectal cancer., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Background: Appropriate surveillance intervals are important to ensure that the benefits of surveillance are not offset by harm. This study aimed to determine the factors associated with nonadherence to recommended colonoscopic surveillance intervals., Methods: The study enrolled 296 patients who underwent screening colonoscopy. The colonoscopies were performed by four endoscopists in the first or second year of fellowship. After each procedure, the endoscopists responded to a questionnaire that elicited information on the degree of concern for missed polyps (using a visual analog scale [VAS]), colonoscopic technical factors, and surveillance intervals., Results: Of the 296 patients, 105 (36%) were adherent and 191 (64%) and were nonadherent to the guidelines. There were no differences in insertion time, withdrawal time, or polyp detection rate between the adherence and nonadherence groups. The endoscopy at cecal intubation was longer in the nonadherence group than in the adherence group (P = 0.013). The proportion of patients with poor bowel preparation was higher in the nonadherence group than in the adherence group (P = 0.011). The endoscopist's concern for missed polyps was greater in the nonadherence group than in the adherence group (P < 0.001). Based on multivariate analysis, only the endoscopist's concern was an independent factor associated with adherence to guidelines (P = 0.008). Poor bowel preparation, loop formation, and colonoscopy experience were independent factors associated with a high concern for missed polyps., Conclusions: Nonadherence to the recommended guidelines was associated with the endoscopist's concern for missed polyps. Improving colonoscopic skills and bowel preparation may decrease nonadherence to the recommended postpolypectomy surveillance interval.