Abstract A 77‐year‐old male patient underwent esophagogastroduodenoscopy at his family doctor, and an easily hemorrhagic depressed lesion was noted near the anterior wall of the gastric antrum. A biopsy revealed moderately differentiated tubular adenocarcinoma > poorly differentiated adenocarcinoma, and the patient was referred to our department for further examination. A 15‐mm 0–IIc lesion is seen near the anterior wall of the gastric antrum and narrow band imaging magnifying endoscopy revealed obscured glandular duct structures and corkscrew pattern vascular structures. We diagnosed the patient with early‐stage gastric cancer [L, Ant, 15mm, cType0‐IIc, cT1(M‐SM1), cN0, cM0, cStage IA] after an esopahogastroduodenoscopy examination at our hospital, and endoscopic submucosal dissection was performed. Histopathological images with hematoxylin and eosin staining showed tumor cells with pale cytoplasm and the immunostaining for alpha‐fetoprotein, sal‐like protein 4, and Glypican3 was positive. The patient was pathologically diagnosed with gastric adenocarcinoma with enteroblastic differentiation, pT1b1 (SM, 0.4 mm), type 0–IIc, 15 mm, UL (‐), Ly0, and V0. Gastric adenocarcinoma with enteroblastic differentiation is one of the representative histological types of alpah‐fetoprotein‐producing gastric cancer. Alpha‐fetoprotein‐producing gastric cancer is infrequent, accounting for at least 3% of all gastric cancers, and is generally highly malignant. Most cases are already advanced upon diagnosis, and finding them in the early stage is rare. Therefore, pathological findings that may indicate the gastric adenocarcinoma with enteroblastic differentiation should be noted even in early gastric cancer.

To investigate endoscopic management and clinical outcomes in patients with non-variceal upper gastrointestinal (GI) bleeding during the coronavirus disease 2019 pandemic. We retrospectively analyzed the data of 332 patients with non-variceal upper GI bleeding who underwent emergency upper GI endoscopy at three hospitals during the pandemic (April 2020-June 2021) and before the pandemic (January 2019-March 2020). The number of emergency upper GI endoscopies, time from hospital arrival to endoscopy, mortality within 30 days, rebleeding within 30 days, interventional radiology (IVR)/surgery requirement, composite outcome, rates of endoscopic hemostasis procedures, and second-look endoscopy were investigated using logistic regression. Overall, 152 and 180 patients underwent emergency upper GI endoscopies during and before the pandemic, respectively. The mean time from arrival to endoscopy was longer during the pandemic than before it (11.7 vs. 6.1h, p<0.01). Multivariate analysis revealed that mortality within 30 days (odds ratio [OR]: 2.27, p=0.26), rebleeding within 30 days (OR: 0.43, p=0.17), IVR/surgery requirement (OR: 1.79, p=0.33), and composite outcome (OR: 0.98, p=0.96) did not differ significantly between the periods; conversely, endoscopic hemostasis procedures (OR: 0.38, p<0.01) and second-look endoscopies (OR: 0.04, p<0.01) were less likely to be performed during the pandemic than before it. Although the time from arrival to endoscopy was significantly longer during the pandemic, it did not affect mortality and rebleeding.

The usefulness of 0.6% sodium alginate (SA) as a submucosal (SM) injection solution for endoscopic SM dissection (ESD) has gained attention over the past few years. However, using ESD for colorectal neoplastic lesions is not explicitly researched as yet. Thus, we conducted this study to determine the feasibility and safety of 0.6% SA solution for colorectal ESD. In this single-center, retrospective pilot study, a total of 100 cases treated with ESD using 0.6% SA as a SM injection solution for colorectal neoplasia at our institute were retrospectively reviewed to clarify the clinical feasibility and safety of 0.6% SA. The primary endpoint was to evaluate the complication rate, and the secondary endpoint was to determine the procedure time and the amount of solution used. Intraoperative perforation was observed in 1 case (1.0%), 2 cases (2.0%) presented with postprocedural hemorrhage, and no lethal adverse events were observed. The median ESD procedure times were 39.5min (10-150), and the amount of solution used was less than 20mL in 67 cases (67.0%). En-bloc resection could be achieved in 97 cases (97.0%). Although six cases underwent subsequent surgery due to the deep SM invasion (>1000μm), there were no cases with nodal involvement, confirmed through histopathological evaluation. Our findings indicate that 0.6% SA can potentially ensure safe and secure ESD for colorectal neoplasia.

Underwater endoscopic mucosal resection (UEMR) is a simpler procedure for superficial non-ampullary duodenal epithelial tumors (SNADET) than conventional endoscopic mucosal resection (cEMR). This study aimed to evaluate whether cEMR can be substituted by UEMR for SNADET in terms of effectiveness, safety, and learning curve. A total of 157 consecutive patients with 203 SNADETs ≤20mm in diameter, including 107 lesions resected by cEMR and 96 lesions resected by UEMR, between January 2019 and May 2023, were retrospectively recruited. The treatment outcomes were compared between the cEMR and UEMR groups. The risk factors for incomplete resection by UEMR were analyzed using univariate and multivariate analyses. Lesions in the UEMR group were divided chronologically into five periods; thereafter, the en bloc resection rate and procedure time were compared. No significant differences existed between the cEMR and UEMR groups in the mean procedure time (3.9min vs. 3.6min, p=0.1380) or en bloc resection rate (91% vs. 94%, p=0.4138). No perforation was observed in either group. Tumor size was an independent risk factor for incomplete resection using UEMR (p<0.01). The history of biopsy was not associated with incomplete resection using UEMR. The en bloc resection rate of UEMR was 100% (20/20) in the first period and ranged from 90% to 100% over all periods. UEMR is safe and effective for SNADET ≤20mm, regardless of a history of biopsy, and is easy to learn. Thus, UEMR can serve as an alternative to cEMR.

Pseudoinvasion is a phenomenon in which adenomatous tissue deviates into the submucosa with the mucosal lamina propria in colorectal epithelial tumors. A relatively large, stalked, neoplastic lesion of the sigmoid colon is considered at high risk of pseudoinvasion. A few reports have described endoscopic mucosal resection or polypectomy for colorectal tumors with pseudoinvasion, but the vertical margins were not sufficiently assessed. Because a positive margin can be a risk factor for recurrence, endoscopic treatment for pseudoinvasion should be carefully considered. We herein report a case in which even endoscopic submucosal dissection (ESD) was not adequate for curative resection of pseudoinvasion in early colorectal cancer. The endoscopic findings of a 25-mm Type 0-Is lesion in the sigmoid colon suggested a low possibility of carcinoma invasion into the deep submucosa. Although ESD was considered to be indicated in this case, laparoscopic sigmoid colon resection was eventually performed because we observed a broadly pulled muscle layer and an almost undetectable submucosal layer during ESD. The surgical specimen showed that the tumor glands of pseudoinvasion existed beyond the planned ESD dissection line, indicating that the vertical margin would have been positive if we had continued ESD. Whether pseudoinvasion was associated with the infeasibility of ESD remains unclear. This case indicates that diagnosing the presence and depth of pseudoinvasion by magnified endoscopy with narrow-band imaging is challenging and that preoperative examinations, such as endoscopic ultrasound, may be needed for a tumor with a high risk of pseudoinvasion.

Individual treatment strategies for esophageal cancer have been investigated based on the anatomical subsite classification. Accurate subsite classification based on these anatomical landmarks is thus important. We investigated the suitability of the existing endoscopic classification and explored alternative landmarks for esophageal subsite classification. Patients who received endoscopic ultrasonography (and computed tomography scans for surveillance of esophageal cancer treatment or esophageal submucosal tumors were included. Distances between anatomical landmarks, including the inferior cricoid cartilage border, superior border of the sternum, and tracheal bifurcation, were measured using a combination of endoscopic ultrasonography, computed tomography, and other information. The mean (standard deviation) distances from the superior incisor dentition to the pharynx-esophagus, cervical-upper thoracic esophagus, and upper-middle thoracic esophagus boundaries were 16.9 (1.7), 21.7 (1.9), and 29.0 (1.9) cm, respectively. However, variances in the differences between the mean and individual distances were large (2.8, 3.4, and 3.7, respectively), mainly because of differences in body height. However, variances in the differences between individual distances and novel endoscopic landmarks, including the lower end of the pyriform sinus and lower end of compression of the left main bronchus, were lower (1.7, 1.2, and 0.6, respectively). Existing indicators of esophageal subsite boundaries were not consistent with anatomical boundaries. Modification of the distance from the superior incisor dentition based on average distances from anatomical landmarks or the use of alternative endoscopic landmarks is recommended to provide more suitable anatomical boundaries.

Double-pigtail stents are commonly used for drainage in cholangitis to prevent stent migration. We report a case in which a double pigtail stent had migrated proximally into the bile duct and was successfully retrieved after endoscopic papillary large balloon dilatation (EPLBD). An 86-year-old man underwent endoscopic papillary sphincterotomy for cholangitis due to common bile duct stones and had a double-pigtail stent placed in the common bile duct. The patient presented a week later for endoscopic biliary stone removal, but the stent had migrated proximally and could not be visualized during the endoscopy. Endoscopic papillary large balloon dilatation was performed to dilate the papilla to a diameter of 12 mm, following which the stent was grasped and removed. The biliary calculi were subsequently extracted, and the procedure was completed without any complications. This case highlights the potential usefulness of endoscopic papillary large balloon dilatation for retrieving a double-pigtail stent that has migrated to the bile duct.

Hepatocellular carcinoma invasion of the bile duct is rare and has a poor prognosis. A 77-year-old man presented at the emergency department with persistent pain in the right hypochondrium. Blood tests and imaging studies revealed a 70-mm occupying lesion in the right lobe of the liver and dilated intrahepatic bile ducts. He was diagnosed with obstructive jaundice and cholangitis. Imaging studies showed an internal mass with poor contrast effects. A liver biopsy was performed to confirm the diagnosis and hepatocellular carcinoma was suspected. Endoscopic retrograde cholangiopancreatography, endoscopic ultrasound, and peroral cholangioscopy were performed to determine the treatment strategy. The bile duct invasion did not extend to the porta hepatis; therefore, right hepatic lobectomy and radical resection were performed. Bile duct invasion in hepatocellular carcinoma is rare and often difficult to diagnose by computed tomography or conventional endoscopic retrograde cholangiopancreatography. However, endoscopic ultrasound and peroral cholangioscopy enable safe and accurate diagnosis of the extent of invasion.

Pancreatic and biliary diseases encompass a range of conditions requiring accurate diagnosis for appropriate treatment strategies. This diagnosis relies heavily on imaging techniques like endoscopic ultrasonography and endoscopic retrograde cholangiopancreatography. Artificial intelligence (AI), including machine learning and deep learning, is becoming integral in medical imaging and diagnostics, such as the detection of colorectal polyps. AI shows great potential in diagnosing pancreatobiliary diseases. Unlike machine learning, which requires feature extraction and selection, deep learning can utilize images directly as input. Accurate evaluation of AI performance is a complex task due to varied terminologies, evaluation methods, and development stages. Essential aspects of AI evaluation involve defining the AI's purpose, choosing appropriate gold standards, deciding on the validation phase, and selecting reliable validation methods. AI, particularly deep learning, is increasingly employed in endoscopic ultrasonography and endoscopic retrograde cholangiopancreatography diagnostics, achieving high accuracy levels in detecting and classifying various pancreatobiliary diseases. The AI often performs better than doctors, even in tasks like differentiating benign from malignant pancreatic tumors, cysts, and subepithelial lesions, identifying gallbladder lesions, assessing endoscopic retrograde cholangiopancreatography difficulty, and evaluating the biliary strictures. The potential for AI in diagnosing pancreatobiliary diseases, especially where other modalities have limitations, is considerable. However, a crucial constraint is the need for extensive, high‐quality annotated data for AI training. Future advances in AI, such as large language models, promise further applications in the medical field.

In our previous study, we visualized and systematically evaluated gas leakage from the forceps plug of the gastrointestinal endoscope system using the Schlieren system. In order to minimize the potential risk of infection from gas leakage from the gastrointestinal endoscope, the development of a new forceps plug was considered urgent. In this study, we analyzed the structure of commercially available forceps plugs and attempted to develop new forceps plugs with improvements. Microfocus computed tomography was used to nondestructively analyze the structural changes that occur when forceps are inserted into a commercially available forceps plug. Based on the findings, the basic structure of the newly developed forceps plug was set. We examined the airtightness of these newly developed plugs using the Schlieren system and also compared their fractional resistance with those of commercially available plugs. As a result of the nondestructive analysis, all of the commercially available plugs had a single valve, and the cleavage created in the valve during forceps, insertion was large in the case of plugs with slit-type entrances. In the newly developed forceps plugs, all four types of plugs showed less gas leakage and similar or better usability compared to the commercially available plugs. The structural weaknesses of the existing gastrointestinal endoscopic forceps plugs were identified. Based on the findings, we froze the design of a prototype of a new forceps plug that was airtight and not inferior in usability compared to commercially available plugs.