A novel endoscopic purse-string suture technique, "loop 9", for gastrointestinal defect closure: a pilot study.

BACKGROUND : This study aimed to assess the feasibility and efficacy of the novel loop 9 method of gastrointestinal (GI) defect closure. METHODS : 20 patients underwent a GI procedure that required defect closure. Loop 9 can be delivered through a single instrument channel (3.2 mm) and released at the defect site. After it has been anchored by two clips positioned on opposite sides of the defect edge, the loop 9 is tightened by pulling the end of the suture intraluminally using biopsy forceps. Additional clips are placed to achieve complete closure. The primary outcome was complete closure rate. The secondary outcomes were closure time, sustained closure rate, and adverse events. RESULTS : Complete closure was achieved in 100 % of cases. The mean size of the mucosal defects was 17.5 mm (range 10-55 mm). The median closure time was 14 minutes. The sustained closure rate was 90 %. No adverse events were noted. CONCLUSIONS : The loop 9 technique is feasible and effective in achieving complete and sustained closure of therapeutic endoscopy-related GI defects.

Diagnosis of congenital esophageal stenosis in adults and treatment with peroral endoscopic myotomy.

BACKGROUND: Congenital esophageal stenosis (CES) in adults is a rare disorder that can present as achalasia, particularly in the distal esophagus. We describe the salient features of CES in adults and identify the feasibility and short-term outcomes of peroral endoscopic myotomy (POEM) for CES. METHODS: In this retrospective, single-center case series, we included 6 patients with a "misdiagnosis" of achalasia established elsewhere, ultimately diagnosed with CES and referred to our institution for POEM. Symptom improvement (clinical success rate), defined as an Eckardt Symptom Score (ESS) of <3 at 2-month follow up was assessed. RESULTS: Six patients (median age: 40 [range: 18-58] years; 4 males) were included. A long-standing history of dysphagia, ring-shaped stenosis on endoscopic examination, "lopsided hourglass" sign on barium esophagogram, and high-resolution manometry findings indicated by a compartmentalized intrabolus pressure pattern with distinction between the stenotic area and the lower esophageal sphincter were the salient features identified. POEM could not be completed in the first 2 cases due to technical challenges. All subsequent 4 patients who underwent successful POEM, exhibited improved ESS of ≤3 (clinical success rate 100%) at 2 months post-POEM. CONCLUSIONS: Along with identification of salient features on several diagnostic modalities, a differential diagnosis of CES in adults must be considered in patients presenting with long-standing history of dysphagia arising from childhood and persisting into adulthood. Although favorable short-term outcomes of POEM were achieved, further evaluation is still warranted, and an inexperienced operator should not attempt POEM on CES patients due to its technical difficulties.

Long-term clinical results of per-oral endoscopic myotomy (POEM) for achalasia: First report of more than 10-year patient experience as assessed with a questionnaire-based survey.

Background and study aims Since per-oral endoscopic myotomy (POEM) was introduced in 2010, it has become accepted as one of the standard treatments for esophageal achalasia worldwide. This study aimed to present long-term clinical results of POEM over 10 years and evaluate the technique and outcomes at the institution where it was first used in clinical settings. Patients and methods Questionnaire-based surveys were sent to patients who received POEM in our institution from September 2008 to May 2010. Patient demographics and procedural outcomes and open-ended questions were posed about the postoperative courses, including symptom improvement and recurrence, additional treatments, and post-POEM gastroesophageal reflux disease (GERD) symptoms. Achalasia symptoms and post-POEM GERD symptoms were evaluated with Eckhardt scores and GerdQ systems, respectively. Results Thirty-six consecutive POEMs were performed in that period and 10-year follow-up data were obtained from 15 patients (41.7 %). Although four cases (26.7 %) required additional pneumatic balloon dilatation (PBD), reduction in post-Eckardt scores were observed in 14 cases (93.3 %). GerdQ score was positive in one patient (6.7 %). Proton pump inhibitors (PPI) were taken by four patients (26.7 %) and their symptoms were well-controlled. Conclusions Clinical results of POEM over 10 years were favorable regardless of various factors. Symptoms improved even in patients who required additional treatments, suggesting that POEM plays a significant role in treatment of achalasia.

Simplified endoscopic pressure study integrated system for the diagnosis of gastroesophageal reflux disease.

Endoscopic pressure study integrated system (EPSIS) is a novel tool for the diagnosis of gastroesophageal reflux disease. It enables the evaluation of the function of the lower esophageal sphincter by monitoring intragastric pressure (IGP) while insufflating the stomach during esophagogastroduodenoscopy. EPSIS can predict abnormal acid reflux with high accuracy based on previous studies. IGP was measured by inserting through the working channel of the scope an intragastric catheter connected to a pressure measuring device. Herein, we assess the feasibility of an updated EPSIS system, which can be performed just by connecting a flush tube to the working channel. This method does not require inserting foreign objects in the stomach and spares catheter insertion in order to simplify the procedure and reduce costs. A single-center pilot study was conducted to evaluate the association between catheter-based EPSIS and the updated EPSIS. The results of EPSIS in 20 patients who underwent both methods were assessed. In all cases, the waveform pattern of IGP measured by catheter-based EPSIS and updated EPSIS was consistent with 15 uphill pattern and five flat pattern. Intraobserver agreement of waveform pattern was perfect between two examiners with kappa value = 1. Intraclass correlation coefficient (ICC) for intraobserver reliability for maximum IGP was excellent with 0.91 (95% confidence interval [CI] of 0.77 < ICC < 0.96) and for pressure gradient was also good with 0.89 (95% CI of 0.71 < ICC < 0.95). In conclusion, our study suggests that the updated EPSIS can be performed without the use of a catheter.

Diagnostic yield of fourth-generation endocytoscopy for esophageal squamous lesions using a modified endocytoscopic classification.

OBJECTIVES: Endocytoscopy (EC) is an ultra-high magnification endoscopy designed to provide in vivo histologic assessment. This study aimed to evaluate the diagnostic yield of the newly developed fourth-generation EC for esophageal squamous lesions by using a modified EC classification. METHODS: A total of 2548 EC images of 57 esophageal targeted areas between June 2015 and October 2017 were retrospectively collected. Two lesions with low-quality images were excluded. Only EC images were independently reviewed by two expert and two non-expert endoscopists. The lesions were classified according to a three-tier modified EC classification. We used a multilevel logistic regression to analyze the data. RESULTS: The sensitivity and specificity of diagnosing non-squamous cell cancer (SCC) vs SCC were 82.5% and 83.0% by the experts; 90.1% and 75.0% by non-experts. The interobserver agreement among the four raters was good (kappa statistic 0.59). The diagnostic accuracy of experts and non-experts was similar (P = 0.16 for specificity and P = 0.20 for sensitivity). The sensitivity and specificity of EC for non-neoplasia vs neoplasia were 88.7% and 74.6% by experts; 90.3 and 52.1% by non-experts. The interobserver agreement among the four raters was moderate (kappa statistic 0.44). The specificity of experts was higher compared to non-experts, although the difference did not reach statistical significance (P = 0.08 for specificity and P = 0.93 for sensitivity). CONCLUSIONS: Fourth-generation EC offers acceptable diagnostic accuracy and reliability in both experts and non-experts, especially when diagnosing SCC lesions.

Importance of second-look endoscopy after per-oral endoscopic myotomy for safe postoperative management.

OBJECTIVES: Per-oral endoscopic myotomy (POEM) is a safe and effective treatment for achalasia and esophageal motility disorders. The role of second-look endoscopy (SE) on postoperative day 1 has not been examined. This study aimed to evaluate the findings and need of SE after POEM. METHODS: This is a single-center, retrospective study. All consecutive patients who underwent POEM and SE on postoperative day 1 between December 2017 and September 2019 were included. The primary endpoint was the rate of newly-detected adverse events (nAE) during SE that required endoscopic intervention or deviation from the normal postoperative course. Multivariate logistic regression was used to identify predictors of nAE. RESULTS: Four-hundred-ninety-seven patients (mean age, 50.3 years; female, 49.9%) were included. SE identified abnormal findings in a total of 71 patients (14.3%). nAE which required endoscopic intervention or deviation from the normal postoperative course were identified in 12 patients (2.4%): eight (1.6%) entry site dehiscence; two (0.4%) submucosal hemorrhage or hematoma; and two (0.4%) dehiscence of an intraoperative perforation site after endoclip closure. Other findings such as mucosal thermal damage without perforation and small submucosal hematoma were found in 54 patients (10.9%) and five patients (1.0%), respectively. Multivariate analysis showed that longer operation time and intraoperative adverse events (AE) were associated with clinically significant nAE during SE. CONCLUSIONS: Second-look endoscopy can detect and treat nAE that may lead to severe AE. Thus, SE should be highly considered before starting oral ingestion in all cases, and especially in those who present an intraoperative AE and longer operation time.

Endoscopic treatment of proton pump inhibitor-refractory gastroesophageal reflux disease with anti-reflux mucosectomy: Experience of 109 cases.

OBJECTIVES: Some patients with gastroesophageal reflux disease (GERD) are refractory to proton pump inhibitor (PPI) therapy. Anti-reflux mucosectomy (ARMS) is a minimally invasive endoscopic procedure for treatment of GERD. In this study, we retrospectively evaluated the outcomes of ARMS performed in patients with PPI-refractory GERD at our institution. METHODS: A total of 109 patients with PPI-refractory GERD who underwent ARMS were retrospectively reviewed. Pre- and post-ARMS questionnaire scores, acid exposure time (AET), DeMeester score, proximal extent, and PPI discontinuation rate were compared. RESULTS: There was a significant improvement in the symptom score (P < 0.01) and 40-50% of patients were able to discontinue PPI after ARMS. In patients who were followed up for 3 years, sustained improvement in subjective symptoms was observed. AET and DeMeester score significantly improved after ARMS (P < 0.01); however, there was no significant improvement in proximal extent (P = 0.0846). CONCLUSIONS: Anti-reflux mucosectomy is an effective minimally invasive therapy for patients with PPI-refractory GERD. The therapeutic efficacy is attributable to suppression of acid backflow due to contraction of the scar tissue in cardia.

Characterization of intragastric pressure waveform in endoscopic pressure study integrated system: Novel diagnostic device for gastroesophageal reflux disease.

OBJECTIVES: Endoscopic pressure study integrated system (EPSIS) is a novel diagnostic tool for gastroesophageal reflux disease (GERD). EPSIS has been developed to evaluate lower esophageal sphincter function by monitoring the intragastric pressure (IGP) while insufflating the stomach during gastroscopy. Based on previous data, EPSIS could diagnose GERD with good accuracy by assessing IGP waveform pattern. This study aimed to further characterize the waveform to improve the diagnostic yield of EPSIS. METHODS: We conducted a retrospective analysis of patients with typical GERD symptoms who underwent both EPSIS and 24-h impedance-pH monitoring (MII-pH) at a single tertiary referral center from October 2018 to May 2020. EPSIS was performed by using a through-the-scope catheter connected to the pressure measuring system (TR-W550, TR-TeH08, AP-C35; Keyence, Osaka, Japan) to monitor IGP. Abnormal acid reflux was defined as acid exposure time (AET) over 6.0%. Pressure waveform was characterized as follows: (i) Basal IGP, (ii) Maximum IGP, (iii) Pressure difference, (iv) Gradient of the waveform. RESULTS: A total of 57 patients with GERD symptoms were analyzed. Twenty-one patients presented abnormal AET on MII-pH. Among EPSIS parameters, pressure difference during insufflation correlated with AET (ρ = -0.66, P < 0.01) and showed the best diagnostic accuracy for AET with the cutoff value of 4.7 mmHg (area under the curve [AUC], 0.87). The gradient of EPSIS waveform also revealed good diagnostic accuracy for abnormal AET with the cutoff value of 0.07 mmHg/s (AUC, 0.81). CONCLUSIONS: Endoscopic pressure study integrated system waveform parameters, especially pressure difference, presented high diagnostic accuracy for the presence of abnormal acid reflux.

Flexible endoscopic strategies for the difficult esophageal stricture.

PURPOSE OF REVIEW: Benign strictures of the esophagus, caused by various causes, are frequently encountered in clinical practice. Although endoscopic dilation is still the standard and first-line therapy, complex and difficult esophageal strictures are still encountered and remain a challenge to endoscopists. The main scope of this review article is to offer a closer look at the different endoscopic modalities and approaches to complex and difficult esophageal strictures. RECENT FINDINGS: In the past few years, endoscopic dilatation, stents including self-expandable and biodegradable types, incisional therapy, and pharmacological treatments have been utilized in the prevention and management of refractory and recurrent esophageal strictures. Meanwhile, more recent techniques such as the BougieCap, percutaneous transgastric endoscopic myotomy, through-the-scope stents, radial incision and cutting, etc. have been developed as alternative methods. A number of studies utilizing these newer methods have shown promising results in the treatment of complex and difficult esophageal strictures. SUMMARY: Endoscopic treatment of refractory, complex and difficult esophageal strictures still remains to be a challenge for many endoscopists. While balloon or bougie dilatation still remains to be the first-line approach, other techniques have emerged as treatment alternatives and may become adjunct therapy to endoscopic dilatation.

Endocytoscopy: technology and clinical application in upper gastrointestinal tract.

Over the past few years, the innovative field of magnifying endoscopy has been expanding with various cutting-edge technologies, one of which is endocytoscopy, to facilitate improvement in the detection and diagnosis of gastrointestinal lesions. Endocytoscopy is a novel ultra-high magnification endoscopic technique enabling high-quality in-vivo assessment of lesions found in the gastrointestinal tract with the use of intraprocedural stains. The main scope of this review article is to offer a closer look at the latest endocytoscopic technology and its clinical application in the upper gastrointestinal tract, especially in the esophagus and stomach, as well as to introduce readers to our simplified and up-to-date endocytoscopic classification, specifically developed for the esophagus and stomach, for the in-vivo assessment and diagnosis of esophageal and gastric lesions. Despite the good accuracy of endocytoscopy in the diagnosis of esophageal and gastric lesions in recent studies, some challenges still remain (e.g., staining method and standardized endocytoscopic classification). Through continuous evaluation and improvement of methods and skills, these challenges may be overcome thus establishing current techniques and classification, paving the way for further advances in the field of endocytoscopy and magnifying endoscopy. In all, endocytoscopy seems to aid in the in-vivo diagnosis of gastrointestinal tract lesions and may, in the future, revolutionize the field of in-vivo endoscopic diagnosis of gastrointestinal cancer, representing another step towards the so-called optical biopsy.

Endoscopic pressure study integrated system reflects gastroesophageal junction competence in patients with erosive esophagitis and Barrett´s esophagus.

OBJECTIVES: The endoscopic pressure study integrated system (EPSIS) is a novel diagnostic tool for gastroesophageal reflux disease (GERD) by monitoring intragastric pressure (IGP). Evaluation of the lower esophageal sphincter (LES) function may be achieved endoscopically by utilizing this newly developed diagnostic tool. This study aimed to evaluate the association between EPSIS results and gastroesophageal reflux-related diseases, e.g., erosive esophagitis (EE) and Barrett's esophagus (BE). METHODS: This was a retrospective, single-center study. All patients who underwent EPSIS between November 2016 and July 2018 were included. EPSIS was performed during esophagogastroduodenoscopy with a dedicated electronic device and a through-the-scope catheter. The maximum IGP (IGP-max) and IGP waveform pattern (flat or uphill) were recorded with this system. Evaluation of an EE and BE was based on the Los Angeles classification and Prague classification, respectively. RESULTS: A total of 104 patients were enrolled; 29 (28%) had EE and 42 (40%) had BE. Patients with EE had lower IGP-max values (16.0 vs 18.8 mmHg, P = 0.01) and an EPSIS flat pattern was seen more frequently (82.8% vs 37.3%, P < 0.001). Similarly, patients with BE displayed a lower IGP-max (15.7 vs 19.6 mmHg, P < 0.001) and presented with an EPSIS flat pattern in a higher proportion (69% vs 37.1%, P < 0.001). These differences remained significant on multivariate analysis. CONCLUSIONS: The EPSIS, as a novel diagnostic tool, was shown to exhibit a relation with EE and BE, implying that EPSIS is a promising modality to evaluate gastroesophageal reflux-related diseases and LES function endoscopically.

Anti-reflux mucosal ablation (ARMA) as a new treatment for gastroesophageal reflux refractory to proton pump inhibitors: a pilot study.

Background The incidence of proton pump inhibitor (PPI)-refractory gastroesophageal reflux disease (GERD) has been increasing. While surgical intervention with Laparoscopic Nissen Fundoplication remains the gold standard, less invasive anti-reflux interventions are desired. We have developed a minimally invasive anti-reflux mucosal ablation (ARMA) treatment. Herein, we report its technical details and describe its feasibility, safety, and efficacy in PPI-refractory GERD. Methods We conducted a prospective single-center single-arm interventional trial evaluating the outcome of ARMA in 12 patients with PPI-refractory GERD. GERD-Health Related Quality of Life Questionnaire (GERD-HRQL) evaluation, Frequency Scale for the Symptoms of GERD (FSSG) assessment, and impedance-pH monitoring were performed at baseline and at 2 months post-ARMA. Results A total of 12 patients underwent ARMA with a median follow-up duration of 9 months (range: 6 - 14 months). Median GERD-HRQL score significantly improved from 30.5 to 12 ( P  = 0.002); median FSSG score significantly improved from 25 to 10.5 ( P  = 0.002), and median DeMeester score decreased from 33.5 to 2.8 ( P  = 0.049) at 2 months follow-up. No immediate complications were observed. Conclusion Our pilot study has shown that ARMA, a new endoscopic treatment for PPI-refractory GERD, is simple, safe, and improves GERD-related symptoms and objective acid reflux parameters.

Clinical outcomes of per-oral endoscopic tumor resection for submucosal tumors in the esophagus and gastric cardia.

OBJECTIVES: The clinical success of per-oral endoscopic myotomy (POEM) has led to the development of a new field of 'submucosal endoscopy'. This study aimed to evaluate the safety, efficacy, and limitations of per-oral endoscopic tumor resection (POET) in the management of submucosal tumors (SMTs) in the esophagus and the gastric cardia. METHODS: POET was performed in 47 patients from January 2011 to December 2017. The indication for POET was SMTs ≤ 30 mm in minor axis diameter. Patient and tumor characteristics (age, gender, tumor location, size, and histology), operative and clinical results of POET (procedure time and completion rate, en bloc resection rate, length of hospitalization, adverse events and tumor recurrence) were analyzed retrospectively. RESULTS: POET was successfully completed in 43 patients (91.5%) without any major adverse events (Clavien-Dindo IIIb-IV). Four patients required conversion to an open surgical procedure due to suboptimal visualization during POET. Four patients underwent piecemeal resection of their SMTs including GISTs. Median follow-up was 44 months (10-96 months), during that time, there were no incidences of tumor recurrence. Tumors that had a minor axis diameter > 30 mm or a tumor mass index (TMI) [major axis diameter (mm) × minor axis diameter (mm)] >1000 had a high likelihood of being converted to surgical resection. CONCLUSIONS: POET is a safe and effective treatment for SMTs. However, in patients where the minor axis diameter is > 30 mm or the TMI > 1000, surgical excision should be considered. Furthermore, application of POET for SMTs with malignant potential should be carefully considered to ensure optimal oncologic outcomes.

Combination of laparoscopic and endoscopic approaches for neoplasia with non-exposure technique (CLEAN-NET) for gastric submucosal tumors: updated advantages and limitations.

Laparoscopic and endoscopic cooperative surgery (LECS) for gastric submucosal tumors (SMTs) has been developed under the concept of resecting gastric tumors with both complete curability and preserving organ functions. Precise resection is obtained by classical LECS, however, concerns regarding intraoperative bacterial infection and dissemination of the tumor cells into the abdominal cavity by LECS with exposure technique still remain. To prevent these concerns, several LECS-related procedures with non-exposure techniques, such as combination of laparoscopic and endoscopic approaches for neoplasia with non-exposure technique (CLEAN-NET) and non-exposed endoscopic wall-inversion surgery (NEWS), have been reported to be safe and feasible. Classical LECS, CLEAN-NET, and NEWS have the same concept, however, each has its own different characteristic procedures; exposure or non-exposure technique, inversion of the tumor into or outer the lumen, retrieval of tumor per oral or through the abdominal cavity, and dominance in the role of the endoscopist or the laparoscopic surgeon. Familiarization with these procedure details is important to understand their indications, advantages and limitations, resulting in providing a tailored minimally invasive surgery for patients. The main scope of this review article is to introduce readers to the clinical application, procedure, and results of CLEAN-NET, both from previous literatures and from our experience, as well as to offer a closer look at its advantages and limitations while comparing with other LECS procedures from the viewpoint of introducing CLEAN-NET first.

A novel endoscopic assessment of the gastroesophageal junction for the prediction of gastroesophageal reflux disease: a pilot study.

Background and aim Hiatal hernia and lower esophageal sphincter (LES) dysfunction play major roles in gastroesophageal reflux disease (GERD) pathogenesis. We developed a novel endoscopic assessment to evaluate the gastroesophageal junction (GEJ). This study aims to evaluate the feasibility of this method for the diagnostic prediction of GERD. Methods A retrospective analysis of patients with GERD symptoms who underwent gastroscopy and esophageal pH-impedance monitoring was conducted. The novel assessment evaluated the following in retroflex view: 1) Cardiac Opening (CO): diameter of the opening of the cardia, 2) Sliding Hernia (SH): length from the diaphragmatic crus to the squamocolumnar junction, 3) Scope Holding Time% (SHT%): the percentage of time that the Scope Holding Sign (SHS) was observed out of 30 seconds. The SHS is defined as the lower esophagus holding the endoscope under excessive insufflation. The results of this assessment and that of pH-impedance monitoring were compared. Results In total, 61 patients (mean age ±â€ŠSD, 54.1 ±â€Š16.4 years, 32 males) were enrolled. CO and SH were significantly correlated with acid exposure time (AET) (ρ = 0.36, P  = 0.005, and ρ = 0.36, P  = 0.004). The optimal cutoff of CO for AET > 6 % was 3 cm (Sensitivity = 72.4 %, Specificity = 46.9 %, AUC = 0.64) and that of SH was 2 cm (Sensitivity = 55.2 %, Specificity = 75.0 %, AUC = 0.70). When the population was stratified according to this cutoff, patients with CO > 3 cm and those with SH > 2 cm presented higher AET (15.1 vs 4.1 %, P  = 0.037, and 23.0 vs 3.6 %, P  = 0.026). Optimal cutoff of SHT% for the number of all reflux episodes > 80 was 75 % (Sensitivity = 81.8 %, Specificity = 54.6%, AUC = 0.67). Patients with SHT% < 75 % presented a higher number of all reflux episodes (88 vs 65, P  = 0.014). Sensitivity, specificity, and accuracy of SHT% < 75 % for all reflux episodes > 80 were 81.8 % (95 %CI: 67.7 - 91.8), 54.5% (95 %CI: 40.4 - 64.5), and 68.2 % (95 %CI: 54.0 - 78.1). Conclusion This novel endoscopic assessment of GEJ significantly predicted the presence of GERD and merits further testing in future studies.

Utilizing fourth-generation endocytoscopy and the 'enlarged nuclear sign' for in vivo diagnosis of early gastric cancer.

Background and study aims Fourth-generation endocytoscopy is an ultra-high magnification endoscopic technique designed to provide excellent quality in vivo histologic assessment of gastrointestinal lesions. This study aims to evaluate the diagnostic accuracy of endocytoscopy in early gastric cancer diagnosis. Patients and methods A single-center, retrospective analysis of prospectively collected data from all gastric endocytoscopic examinations was conducted. Two expert endoscopists, blinded to white-light and narrow-band imaging findings as well as histopathologic diagnosis, independently reviewed and diagnosed all endocytoscopic images. A newly recognized "enlarged nuclear sign" was detected, and its implication in early gastric cancer diagnosis was evaluated. The diagnostic performance of fourth-generation endocytoscopy was assessed while using the gold standard histopathology as a reference. Results Forty-three patients (mean age±SD, 72.6 ±â€Š12.1 years; 31 males) were enrolled. Based on histopathology, 23 had well-differentiated adenocarcinomas, four adenomas, and 16 non-neoplastic lesions. The sensitivity, specificity, and accuracy of fourth-generation endocytoscopy for gastric cancer diagnosis were 87.0 % (95 % CI: 67.9 - 95.5), 80.0 % (95 % CI: 58.4 - 91.9), and 83.7 % (95 % CI: 70.0 - 91.9) by endoscopist A; and 91.3 % (95 % CI: 73.2 - 97.6), 75.0 % (95 % CI: 53.1 - 88.8), and 83.7 % (95 % CI: 70.0 - 91.9) by endoscopist B. The inter-observer agreement, Kappa statistic = 0.71 (95 % CI: 0.50 - 0.93), was good. The sensitivity, specificity, and accuracy of the enlarged nuclear sign for early gastric cancer diagnosis were 87.0 % (95 % CI: 67.9 - 95.5), 95.0 % (95 % CI: 76.4 - 99.1), and 90.7 % (95 % CI: 78.4 - 96.3) by endoscopist A; and 82.6 % (95 % CI: 62.9 - 93.0), 85.0 % (95 % CI: 64.0 - 94.8), and 83.7 % (95 % CI: 70.0 - 91.9) by endoscopist B. The inter-observer agreement, Kappa statistic = 0.68 (95 % CI: 0.51 - 0.89) was good. Conclusion: Fourth-generation endocytoscopy appears to aid in the diagnosis of early gastric cancer, particularly well-differentiated adenocarcinomas, due to its good diagnostic accuracy and identification of the "enlarged nuclear sign," and deserves further evaluation in future studies.