Tumor thickness as a novel risk factor for lymph node metastasis by superficial squamous cell carcinoma of head and neck.

Narrow-band imaging combined with magnified endoscopy has enabled the detection of superficial squamous cell carcinoma of the head and neck (SSCCHN) that has been resected with minimally invasive treatment, preserving vocalization and swallowing functions. However, risk factors of lymph node metastasis (LNM) must be identified, as some patients with LNM have a poor prognosis. From an initial 599 patients with 700 lesions who underwent trans-oral surgery in 27 Japanese hospitals (a nationwide registration survey), we enrolled 541 patients with 633 SSCCHNs, as indicated by central pathological diagnoses. All pathological specimens for each patient were examined using 20 pathological factors that are thought to affect the LNM of SSCCHN. In all, 24 (4.4%) of the 568 SSCCHNs exhibited LNM, and all 24 had at least one solitary nest of epithelial neoplastic cells present in the stroma, clearly separated from the intraepithelial carcinoma. Multivariate analysis also showed that tumor thickness (p = 0.0132, RR: 7.85, 95% confidence interval [CI]: 1.54-40.02), and an INFc pattern classified as infiltrating growth (INF) with unclear boundaries between tumor and non-tumor tissues (p = 0.0003, RR: 14.47, 3.46-60.46), and tumor budding (p = 0.0019, RR: 4.35, CI: 1.72-11.01) were significantly associated with LNM. Solitary nests may be indicative of LNM. In addition, tumor thickness was revealed to be a risk factor for LNM in SSCCHNs using pT factors that do not include an invasion depth element because of the anatomical absence of the muscularis mucosae.

Association between colonic adenoma size and proliferative zone in the crypt.

BACKGROUND: We previously reported unusual adenomas with proliferative zones confined to the lower two-thirds of the crypt. The proliferative zones of colorectal adenomas have three patterns: 'lower,' 'superficial' and 'entire'. This study aimed to clarify the characteristics of each adenoma pattern. METHODS: We investigated 2925 consecutive patients who underwent colonoscopy at our institute. All polyps that were removed were histologically examined using hematoxylin and eosin staining. The location of the proliferative zone was assessed for adenomas. Data were compared using Dunn's and Kruskal-Wallis tests. RESULTS: Colorectal adenomas with 'lower' proliferative zone often appeared similar to hyperplastic polyps (42.8%), and the frequency was significantly higher than that of adenomas with 'superficial' and 'entire' proliferative zones (p < 0.001). The mean sizes of adenomas were 2.4, 3.0 and 3.9 mm for 'lower,' 'superficial' and 'entire' proliferative zones, respectively. A significant gradual increase was observed. Regarding morphology, the proportion of type 0-I in adenomas with an 'entire' proliferative zone was significantly higher than that in adenomas with 'superficial' proliferative zone (p < 0.001). CONCLUSION: While colorectal adenomas develop and increase in size, the proliferative zone appears to shift upward and become scattered.

Incidence of sodium-glucose cotransporter-2 inhibitor-associated perioperative ketoacidosis in surgical patients: a prospective cohort study.

PURPOSE: Sodium-glucose cotransporter 2 inhibitors (SGLT2is) are commonly prescribed anti-diabetic medications with various beneficial effects; however, they have also been associated with ketoacidosis. The aim of this study was to determine the incidence of SGLT2i-associated perioperative ketoacidosis (SAPKA) in surgical patients. METHODS: We conducted a multicenter, prospective cohort study across 16 centers in Japan, enrolling surgical patients with diabetes who were prescribed SGLT2is between January 2021 and August 2022. Patients were monitored until the third postoperative day to screen for SAPKA, defined as urine ketone positivity with a blood pH of < 7.30 and HCO3 level ≤ 18.0 mEq/L, excluding cases of respiratory acidosis. RESULTS: In total, 759 of the 762 evaluated patients were included in the final analysis. Among these, three patients (0.40%) had urine ketones with a blood pH of < 7.30; however, blood gas analysis revealed respiratory acidosis in all three, and none of them was considered to have SAPKA. The estimated incidence of SGLT2i-associated postoperative ketoacidosis was 0% (95% confidence interval, 0%-0.4%). CONCLUSIONS: The observed incidence of SAPKA in our general surgical population was lower than expected. However, given that the study was observational in nature, interpretation of study results warrants careful considerations for biases.

Hyperplastic polyp-like adenoma: a subtype of colonic adenoma with a proliferative zone confined to the lower two-thirds of the crypt.

BACKGROUND: The proliferative zone of colonic adenomas is confined to the upper third of the crypt or is scattered along its entire axis. In contrast, there are unusual adenomas with proliferative zones confined to the lower two-thirds of the crypt. We investigated the frequency and endoscopic features of adenomas with lower proliferative zones. METHODS: We retrospectively reviewed consecutive patients who underwent colonoscopies between September 2022 and March 2023 at the Toyoshima Endoscopy Clinic. Colorectal polyps were endoscopically assessed using the Japan Narrow-Band Imaging Expert Team (JNET) classification. All resected polyps were histologically examined, and the proliferative zone locations were assessed in the adenomas. RESULTS: The frequency of adenomas with a lower proliferative zone was 1.8% (44/2420) in adenomas. Among these adenomas, JNET type 1 incidence was 43.2% (19/44), which was significantly higher than that in adenomas with a normal proliferative zone. Adenomas with a lower proliferative zone were diminutive (mean size: 2.5 mm) and prone to develop in the proximal colon. CONCLUSION: Colonic adenomas with proliferative zones confined to the lower two-thirds of the crypt often appear as diminutive, hyperplastic polyps.

Diagnostic criteria and endoscopic and histological findings of autoimmune gastritis in Japan.

The Japanese diagnostic criteria for autoimmune gastritis (AIG) were established by the "Study Group on the establishment of diagnostic criteria for type A gastritis," which is related to a workshop associated with the Japan Gastroenterological Endoscopy Society (JGES) and the Committee of AIG Research Group (CARP). The criteria were set as follows: the cases of confirmed diagnosis are patients in whom either the endoscopic or histological findings, or both, meet the requirements for AIG and who are confirmed to be positive for gastric autoantibodies (either anti-parietal cell or anti-intrinsic factor antibodies, or both). The presentation of endoscopic findings of early-stage AIG in the diagnostic criteria was withheld owing to the need for further accumulation and characterization of endoscopic clinical data. Therefore, diagnosis of early-stage AIG only requires histological confirmation and gastric autoantibody positivity. Suspected cases are patients in whom either the endoscopic or histological findings, or both, meet only the requirements for AIG. Histological findings only meet the requirements for early stage. AIG has been underdiagnosed in the past, but our study group's newly proposed diagnostic criteria will enable a more accurate and early diagnosis of AIG. The criteria can be used to stratify patients into various high-risk groups for gastric tumors and pernicious anemia. They would allow the establishment of an appropriate surveillance system in the coming years. Nevertheless, issues such as establishing the endoscopic findings of early-stage AIG and obtaining Japanese insurance coverage for gastric autoantibody tests require attention.

Sodium-glucose cotransporter 2 inhibitor-associated perioperative ketoacidosis: a systematic review of case reports.

Although the recommended preoperative cessation period for sodium-glucose cotransporter 2 inhibitors (SGLT2is) changed in 2020 (from 24 h to 3-4 days preoperatively) to reduce the risk of SGLT2i-associated perioperative ketoacidosis (SAPKA), the validity of the new recommendation has not been verified. Using case reports, we assessed the new recommendation effectiveness and extrapolated precipitating factors for SAPKA. We searched electronic databases up to June 1, 2022 to assess SAPKA (blood pH < 7.3 and blood or urine ketone positivity within 30 days postoperatively in patients taking SGLT2i). We included 76 publications with 99 cases. The preoperative SGLT2i cessation duration was reported for 59 patients (59.6%). In all cases with available cessation periods, the SGLT2is were interrupted < 3 days preoperatively. No SAPKA cases with > 2-day preoperative cessation periods were found. Many case reports lack important information for estimating precipitating factors, including preoperative SGLT2i cessation period, body mass index, baseline hemoglobin A1c level, details of perioperative fluid management, and type of anesthesia. Our study suggested that preoperative SGLT2i cessation for at least 3 days could prevent SAPKA. Large prospective epidemiologic studies are needed to identify risk factors for SAPKA.

Brown slits for colorectal adenoma crypts on conventional magnifying endoscopy with narrow band imaging using the X1 system.

BACKGROUND: Accurate diagnosis of colorectal premalignant polyps, including adenomas, is vital in clinical practice. AIM: To investigate the diagnostic yields of novel findings of brown slits for adenomas. METHODS: Patients who underwent colonoscopy at the Toyoshima Endoscopy Clinic were enrolled. Polyps sized ≥ 5 mm suspected of adenomas or clinically significant serrated polyps were included in the study. We defined the surface structures of colorectal polyps, which were brown curves inside and along the tubular glands identified using a combination of a new X1 system (Olympus Corporation) and a conventional magnifying colonoscope with non-staining narrow band imaging (NBI), as brown slits. The brown slits corresponded to slit-like lumens on endocytoscopy and histological crypt openings of an adenoma. We evaluated the diagnostic performance of brown slits for adenoma. RESULTS: A total of 108 Lesions from 62 patients were eligible. The average age was 60.4 years and 41.9% were male. The mean polyp size was 7.45 ± 2.83 mm. Fifty-seven lesions were positive for brown slits. Histopathological diagnosis comprised 59 low-grade tubular adenomas, 16 sessile serrated lesions, and 33 hyperplastic polyps. Among 59 adenomas, 56 (94.9%) were positive for brown slits. Among 16 sessile serrated lesions, 0 (0%) was positive for brown slits. Among 33 hyperplastic polyps, 1 (3.0%) was positive for brown slits. The sensitivity, specificity, and accuracy of brown slits for adenoma were 94.9%, 98.0%, and 96.3%, respectively. The positive predictive value and negative predictive value of brown slits for adenoma were also excellent for 98.2%, and 94.1%, respectively. CONCLUSION: Brown slits on conventional magnifying endoscopy with non-staining NBI using the X1 system were useful for diagnosing colorectal adenoma. The new endoscopy system could be examined using new standards.

Postoperative Ketoacidosis With Hypoglycemia in a Nondiabetic Patient Taking Dapagliflozin for Heart Failure: A Case Report.

Sodium-glucose cotransporter 2 (SGLT-2) inhibitors are relatively new antidiabetic drugs, which have been recently approved for heart failure treatment. Although treatment interruption is recommended 3 to 4 days before surgery, it is unclear whether SGLT-2 inhibitors should be discontinued when prescribed for heart failure treatment. We describe a case of postoperative ketoacidosis with hypoglycemia in an 83-year-old woman who took dapagliflozin for heart failure and underwent transcatheter aortic valve replacement. She was nondiabetic and took dapagliflozin on the day of the procedure. This case suggests the need to discontinue SGLT-2 inhibitors ahead of the day of surgery when used for heart failure.

Consistency between the endoscopic Kyoto classification and pathological updated Sydney system for gastritis: A cross-sectional study.

BACKGROUND: Two methods are used to evaluate gastritis: the updated Sydney system (USS) with pathology and Kyoto classification, a new endoscopy-based diagnostic criterion for which evidence is accumulating. However, the consistency of their results is unclear. This study investigated the consistency of their results. METHODS: Patients who underwent esophagogastroduodenoscopy and were evaluated for Helicobacter pylori infection for the first time were eligible. The association between corpus and antral USS scores (neutrophil activity, chronic inflammation, atrophy, and intestinal metaplasia) and Kyoto classification scores (atrophy, intestinal metaplasia, enlarged folds, nodularity, and diffuse redness) was assessed. RESULTS: Seven-hundred-seventeen patients (mean age, 49.2 years; female sex, 57.9%; 450 H. pylori-positive and 267 H. pylori-negative patients) were enrolled. All endoscopic gastritis cases in the Kyoto classification were associated with high corpus and antral USS scores for neutrophil activity and chronic inflammation. A subanalysis was performed for H. pylori-positive patients. Regarding atrophy and intestinal metaplasia, endoscopic findings were associated with USS scores. Enlarged folds, nodularity, and diffuse redness were associated with high corpus USS scores for neutrophil activity and chronic inflammation, but with low antral USS scores for atrophy and intestinal metaplasia. The Kyoto classification scores were also associated with the pathological topographic distribution of neutrophil activity and intestinal metaplasia. CONCLUSIONS: Among H. pylori-positive individuals, endoscopic and pathological diagnoses were consistent with atrophy and intestinal metaplasia. Enlarged folds, nodularity, and diffuse redness were associated with pathological inflammation (neutrophil activity and chronic inflammation) of the corpus; however, they were inversely associated with pathological atrophy and intestinal metaplasia. The endoscopy-based Kyoto classification of gastritis partially reflects pathology.

Decreased anti-parietal cell antibody titer in the advanced phase of autoimmune gastritis.

BACKGROUND: Autoimmune gastritis (AIG) is histologically classified into three phases according to the severity of oxyntic mucosal atrophy: early, florid, and end phases. This study aimed to clarify the relationship between the AIG phase and the anti-parietal cell antibody titer. METHODS: Patients who underwent upper gastrointestinal endoscopy were retrospectively reviewed in this study. We enrolled patients who were histologically diagnosed with AIG and serologically tested for anti-parietal cell antibody (APCA). AIG patients were classified into three groups: early, florid, and end phase groups. Clinical characteristics, including APCA titers, were compared among these three groups. RESULTS: A total of 44 AIG patients were enrolled. There were two patients in the early phase, 11 in the florid phase, and 31 in the end phase. APCA-positive rates were 100% in the early phase, 90.9% in the florid phase, and 90.3% in the end phase. The mean APCA titer was 480 U in the early phase, 220 U in the florid phase, and 150 U in the end phase. There was a stepwise decrease in the APCA titer from the early phase to the end phase. The mean APCA titer for the end phase was significantly lower than that of the early phase or florid phase. Additionally, there was a stepwise decrease in serum gastrin levels from the early phase to the end phase. CONCLUSION: AIG progresses from the early phase to the end phase, and the APCA titer shows a decrease. The negativity of APCA could occur, especially in the end phase.

Clue of Diagnosis for Autoimmune Gastritis.

BACKGROUND: The diagnostic clues for autoimmune gastritis (AIG) can be classified into 2 categories: endoscopic findings and pathological diagnosis. We believe that research on the AIG detection rate by endoscopists could provide a better understanding of the diagnosis of AIG. This study aimed to clarify the ratio of the endoscopic and the pathological diagnoses of AIG. METHODS: We retrospectively reviewed consecutive patients who underwent esophagogastroduodenoscopy (EGD). During their first EGD, the gastric mucosa with C2 atrophy or more was biopsied for pathological evaluation based on the updated Sydney system. A gastric biopsy was also performed after Helicobacter pylori eradication, obtaining specimens from at least 2 sites, the greater curvature of the corpus and the antrum. We enrolled patients who were positive for the anti-parietal cell antibody and were diagnosed with AIG, histologically and/or endoscopically. The detection rates of AIG were compared between endoscopic diagnosis and pathological diagnosis. RESULTS: A total of 10,822 patients underwent EGD during the study period. Finally, 41 patients with AIG were enrolled, leading to an AIG prevalence of 0.38% in this study. As for the clue leading to AIG detection, 31.7% (13/41) were diagnosed through endoscopy (proximal-predominant atrophy), and 68.3% (28/41) were diagnosed pathologically. The AIG detection rate by endoscopists in the posteradication group was significantly lower than in the H. pylori-negative group (p < 0.05). CONCLUSION: Endoscopists frequently overlooked AIG, especially in posteradication cases. Pathological assessment using the updated Sydney system after H. pylori eradication might be a promising strategy to detect AIG better.

Transoral surgery for superficial head and neck cancer: National Multi-Center Survey in Japan.

Head and neck cancers, especially in hypopharynx and oropharynx, are often detected at advanced stage with poor prognosis. Narrow band imaging enables detection of superficial cancers and transoral surgery is performed with curative intent. However, pathological evaluation and real-world safety and clinical outcomes have not been clearly understood. The aim of this nationwide multicenter study was to investigate the safety and efficacy of transoral surgery for superficial head and neck cancer. We collected the patients with superficial head and neck squamous cell carcinoma who were treated by transoral surgery from 27 hospitals in Japan. Central pathology review was undertaken on all of the resected specimens. The primary objective was effectiveness of transoral surgery, and the secondary objective was safety including incidence and severity of adverse events. Among the 568 patients, a total of 662 lesions were primarily treated by 575 sessions of transoral surgery. The median tumor diameter was 12 mm (range 1-75) endoscopically. Among the lesions, 57.4% were diagnosed as squamous cell carcinoma in situ. The median procedure time was 48 minutes (range 2-357). Adverse events occurred in 12.7%. Life-threatening complications occurred in 0.5%, but there were no treatment-related deaths. During a median follow-up period of 46.1 months (range 1-113), the 3-year overall survival rate, relapse-free survival rate, cause-specific survival rate, and larynx-preservation survival rate were 88.1%, 84.4%, 99.6%, and 87.5%, respectively. Transoral surgery for superficial head and neck cancer offers effective minimally invasive treatment. Clinical trials registry number: UMIN000008276.

Massive Leak in CO2 Absorber of Perseus A500 Did Not Inhibit Mechanical Ventilation but Manual Bag Ventilation: A Case Report With Experimental Reproduction.

Massive leaks in the anesthesia circuit may cause intraoperative hypoventilation and awareness; we experienced this with a disposable CO2 absorber in Perseus A500, which uses turbine ventilation to create positive-pressure ventilation. Consequently, manual ventilation was rendered impossible. During prolonged surgeries, CO2 absorbers may be replaced by a new one. In our case, the replacement had an occult leak. Absorbers should be checked before the exchange, and the econometer or reservoir bag's filling state should be monitored. Anesthesia providers should know an anesthesia machine's dynamics and breathing system to provide appropriate management of such a leak.

A single nucleotide polymorphism in Prostate Stem Cell Antigen is associated with endoscopic grading in Kyoto classification of gastritis.

The risk allele of a single nucleotide polymorphism (SNP) rs2294008 in the Prostate stem cell antigen (PSCA) gene is strongly associated with gastric cancer. Although the Kyoto classification score is believed to be an indicator of gastric cancer risk, it lacks supporting genetic evidence. We investigated the effect of this risk allele of PSCA SNP on the Kyoto score. Participants without a history of gastric cancer or Helicobacter pylori (H. pylori) eradication underwent esophagogastroduodenoscopy, H. pylori evaluation, and SNP genotyping. The Kyoto score is the sum of scores obtained from endoscopy-based atrophy, intestinal metaplasia, enlarged folds, nodularity, and diffuse redness. The Kyoto score is novel in the light of scoring for gastritis. A total of 323 patients were enrolled (number of individuals with genotype CC: 52; CT: 140; TT: 131, average age: 50.1 years, male: 50.8%). The patient baseline characteristics including age, sex, body mass index, smoking, drinking, family history of gastric cancer, and H. pylori status had no association with PSCA SNP. The Kyoto score was higher in T (CT or TT genotype; risk allele) carriers than in CC carriers. Atrophy, enlarged folds, and diffuse redness scores were higher in T allele carriers (risk allele) than in CC genotype individuals. In multivariate analysis, the Kyoto score was independently associated with PSCA SNP (OR: 1.30, p = 0.012). Thus, the Kyoto score was associated with a genetic predisposition.

Incisura angularis belongs to fundic or transitional gland regions in Helicobacter pylori-naïve normal stomach: Sub-analysis of the prospective multi-center study.

OBJECTIVE: Incisura angularis is one of the important parts for evaluating mucosal atrophy and cancer risk. We determined the type of mucosa at incisura angularis in Helicobacter pylori-naïve normal stomach. METHODS: Subjects aged 40 years or older who underwent esophagogastroduodenoscopy for dyspepsia or a routine health checkup were recruited in 24 facilities between March 2008 and February 2009. Serum antibody to H. pylori was measured. Endoscopic atrophy was evaluated according to Updated Kimura-Takemoto classification. Five biopsy specimens were taken from the incisura angularis and greater and lesser curvatures of the antrum and corpus. These specimens were histologically classified as fundic, pyloric or transitional. H. pylori-naïve normal stomach was defined with the strictest criterion among various combinations of histological, endoscopic and serum findings. We determined histological type of mucosa at incisura angularis in H. pylori-naïve normal stomach. RESULTS: A total of 270 subjects (122 men, mean 64.6 yo) were analyzed. The strictest criterion consists of serum antibody ≤ 3.0 U/mL, endoscopic atrophy C-1 and histological grade 0 in all of the five items in Updated Sydney System. The numbers having fundic, transitional and pyloric mucosa at incisura angularis under the strictest criterion were 13 (50%), 13 (50%) and 0, respectively. The probability that the type of mucosa at incisura angularis would be pyloric was almost zero (97.5% confidence interval 0-0.132). CONCLUSIONS: Incisura angularis of the stomach may not belong to pyloric, but fundic or transitional mucosa in H. pylori-naïve normal stomach. UMIN000018218.

Endoscopy-based Kyoto classification score of gastritis related to pathological topography of neutrophil activity.

BACKGROUND: Endoscopy-based Kyoto classification for gastritis and pathological topographic distribution of neutrophil infiltration are correlated with gastric cancer risk. AIM: To investigate the association between Kyoto classification and the topographic distribution of neutrophil activity. METHODS: Kyoto classification score, ranging from 0 to 8, consisted of atrophy, intestinal metaplasia, enlarged folds, nodularity, and diffuse redness. Neutrophil activity was scored according to the updated Sydney System using biopsy samples obtained from the greater curvature of the corpus and the antrum. The participants were divided into four categories, inactive stomach, antrum-predominant gastritis, pangastritis, and corpus-predominant gastritis, based on the topographic distribution of neutrophil activity. Effects of sex, age, body mass index, drinking habit, smoking habit, family history of gastric cancer, serum Helicobacter pylori (H. pylori) antibody, and Kyoto score on topography of neutrophil infiltration were analyzed. RESULTS: A total of 327 patients (comprising 50.7% women, with an average age of 50.2 years) were enrolled in this study. H. pylori infection rate was 82.9% with a mean Kyoto score of 4.63. The Kyoto score was associated with the topographic distribution of neutrophil activity. Kyoto scores were significantly higher in the order of inactive stomach, antrum-predominant gastritis, pangastritis, and corpus-predominant gastritis (3.05, 4.57, 5.21, and 5.96, respectively). Each individual score of endoscopic findings (i.e., atrophy, intestinal metaplasia, enlarged folds, nodularity, and diffuse redness) was correlated with the topographic distribution of neutrophil activity. On multivariate analysis, the Kyoto score, age, and serum H. pylori antibody were independently associated with the topographic distribution of neutrophil activity. CONCLUSION: The Kyoto classification score was associated with the topographic distribution of neutrophil activity.

Nodularity-like appearance in the cardia: novel endoscopic findings for Helicobacter pylori infection.

Background and study aims Helicobacter pylori -associated nodular gastritis, which is associated with follicular lymphoid hyperplasia, is mainly recognized in the antrum. However, we have also observed nodularity-like appearance in the cardia. This study aimed to investigate the clinical significance of cardiac nodularity-like appearance in H. pylori -associated gastritis. Patients and methods Patients who underwent esophagogastroduodenoscopy and were evaluated for H. pylori infection for the first time were enrolled. A nodularity-like appearance in the cardia was defined as a miliary nodular appearance or scattered appearances of small circular whitish coloration. H. pylori infection was diagnosed according to serum anti- H. pylori antibody and the urea breath test or histology. Accuracy of the H. pylori infection diagnoses based on nodularity-like appearance were assessed. Results Among 265 patients, 42 patients (15.8 %) were diagnosed as positive for H. pylori . Cardiac nodularity-like appearance and antral nodularity were recognized in 25 and 15 patients, respectively. In accuracy of predicting H. pylori by cardiac nodularity-like appearance, specificity was 0.996, sensitivity was 0.571, positive predictive value was 0.960, negative predictive value was 0.925, and accuracy was 0.928. The sensitivity of cardiac nodularity-like appearance was significantly higher than that of antral nodularity ( P  = 0.0284). Conclusions Cardiac nodularity-like appearance had a high accuracy rate for H. pylori infection diagnosis. Cardiac nodularity-like appearance was found more frequently than antral nodularity.

Expert endoscopists with high adenoma detection rates frequently detect diminutive adenomas in proximal colon.

Background and study aims Adenoma detection rate (ADR) is an important quality indicator in colonoscopy, and improved ADR decreases the incidence of colorectal cancer. We investigated differences in polyp detection according to the endoscopist's ADR. Patients and methods We performed a propensity-score matching study using baseline patient characteristics of age, sex, body mass index, family history of colorectal cancer, smoking, drinking, indication for colonoscopy, bowel preparation, and colonoscope type. We compared polyp detection and colonoscopy procedures between patients who underwent colonoscopy by high-ADR endoscopists (high ADR group) and by low-ADR endoscopists (low ADR group). Results We matched 334 patients in the high ADR group with 334 in the low ADR group. The ADR was 44.0 % and 26.9 % for the high-ADR and low-ADR endoscopists, respectively. Proximal, nonprotruding, and diminutive adenomas were more frequently detected by high-ADR endoscopists than by low-ADR endoscopists (all P  < 0.001); similarly, more high-risk adenomas were detected by high-ADR endoscopists ( P  = 0.028). Furthermore, more sessile serrated polyps detected by high-ADR endoscopists ( P  = 0.041). High-ADR endoscopists more frequently performed pancolonic chromoendoscopy ( P  < 0.001). Conclusions Expert detectors often found nonprotruding and diminutive adenomas in the proximal colon along with increased detection rate of high-risk adenomas. Low-ADR endoscopists need to recognize the features of missed adenomas to improve their ADRs.