Value of artificial intelligence with novel tumor tracking technology in the diagnosis of gastric submucosal tumors by contrast-enhanced harmonic endoscopic ultrasonography.

BACKGROUND AND AIM: Contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) is useful for the diagnosis of lesions inside and outside the digestive tract. This study evaluated the value of artificial intelligence (AI) in the diagnosis of gastric submucosal tumors by CH-EUS. METHODS: This retrospective study included 53 patients with gastrointestinal stromal tumors (GISTs) and leiomyomas, all of whom underwent CH-EUS between June 2015 and February 2020. A novel technology, SiamMask, was used to track and trim the lesions in CH-EUS videos. CH-EUS was evaluated by AI using deep learning involving a residual neural network and leave-one-out cross-validation. The diagnostic accuracy of AI in discriminating between GISTs and leiomyomas was assessed and compared with that of blind reading by two expert endosonographers. RESULTS: Of the 53 patients, 42 had GISTs and 11 had leiomyomas. Mean tumor size was 26.4 mm. The consistency rate of the segment range of the tumor image extracted by SiamMask and marked by the endosonographer was 96% with a Dice coefficient. The sensitivity, specificity, and accuracy of AI in diagnosing GIST were 90.5%, 90.9%, and 90.6%, respectively, whereas those of blind reading were 90.5%, 81.8%, and 88.7%, respectively (P = 0.683). The κ coefficient between the two reviewers was 0.713. CONCLUSIONS: The diagnostic ability of CH-EUS results evaluated by AI to distinguish between GISTs and leiomyomas was comparable with that of blind reading by expert endosonographers.

Utility of contrast-enhanced harmonic endoscopic ultrasonography for T-staging of patients with extrahepatic bile duct cancer.

BACKGROUND: The value of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) for T-staging in patients with extrahepatic bile duct cancer was evaluated. METHODS: This single-center, retrospective study included consecutive patients with extrahepatic bile duct cancer who underwent surgical resection after preoperative EUS, CH-EUS, and contrast-enhanced CT (CE-CT) examinations between June 2014 and August 2017. The capacity of these modalities for T-staging of extrahepatic bile duct cancer was evaluated by assessing invasion beyond the biliary wall into the surrounding tissue, gallbladder, liver, pancreas, duodenum, portal vein system (portal vein and/or superior mesenteric vein), inferior vena cava, and hepatic arteries (proper hepatic artery, right. and/or left. hepatic artery). Blind reading of EUS, CH-EUS, and CE-CT images was performed by two expert reviewers each. RESULTS: 38 patients were eligible for analysis, of which eight had perihilar bile duct cancer and 30 had distal bile duct cancer. Postoperative T-staging was T1 in 6, T2 in 16, and T3 in 16 cases. CH-EUS was superior to CE-CT for diagnosing invasion beyond the biliary wall into surrounding tissue (92.1% vs. 45.9%, P = 0.0002); the ability to detect invasion to other organs did not differ significantly between the two modalities. The accuracy of CH-EUS for T-staging of tumors was better than that of CE-CT (73.7% vs. 39.5%, P = 0.0059). CH-EUS tended to have a better accuracy than EUS for the diagnosis of invasion beyond the biliary wall into the surrounding tissue (92.1% vs. 78.9%, P = 0.074) and T-staging (73.7% vs. 60.5%, P = 0.074). CONCLUSION: CH-EUS is useful for T-staging of extra hepatic bile duct cancer, especially in terms of invasion beyond the biliary wall into the surrounding tissue.

Comparison of radiation exposure between endoscopic ultrasound-guided drainage and transpapillary drainage by endoscopic retrograde cholangiopancreatography for pancreatobiliary diseases.

OBJECTIVES: The transpapillary drainage by endoscopic retrograde cholangiopancreatography (ERCP-D) cannot be performed without fluoroscopy, and there are many situations in which fluoroscopy is required even in endoscopic ultrasound-guided drainage (EUS-D). Previous studies have compared the efficacy, but not the radiation exposure of EUS-D and ERCP-D. While radiation exposure in ERCP-D has been previously evaluated, there is a paucity of information regarding radiation doses in EUS-D. This study aimed to assess radiation exposure in EUS-D compared with that in ERCP-D. METHODS: This retrospective single-center cohort study included consecutive patients who underwent EUS-D and ERCP-D between October 2017 and March 2019. The air kerma (AK, mGy), kerma-area product (KAP, Gycm2 ), fluoroscopy time (FT, min), and procedure time (PT, min) were assessed. The invasive probability weighting method was used to qualify the comparisons. RESULTS: We enrolled 372 and 105 patients who underwent ERCP-D and EUS-D, respectively. The mean AK, KAP, and FT in the EUS-D group were higher by 53%, 28%, and 27%, respectively, than those in the ERCP-D group, whereas PT was shorter by approximately 11% (AK, 135.0 vs. 88.4; KAP, 28.1 vs. 21.9; FT, 20.4 vs. 16.0; PT, 38.7 vs. 43.5). The sub-analysis limited to biliary drainage cases showed the same trend (AK, 128.3 vs. 90.9; KAP, 27.0 vs. 22.2; FT, 16.4 vs. 16.1; PT, 32.5 vs. 44.4). CONCLUSIONS: This is the first study to assess radiation exposure in EUS-D compared with that in ERCP-D. Radiation exposure was significantly higher in EUS-D than in ERCP-D, despite the shorter procedure time.

Improved detection of liver metastasis using Kupffer-phase imaging in contrast-enhanced harmonic EUS in patients with pancreatic cancer (with video).

BACKGROUND AND AIMS: Kupffer-phase imaging visualized by perfluorobutane (Sonazoid) distribution into normal liver tissues upon phagocytosis by Kupffer cells potentially aids in improving detection of liver metastasis compared with fundamental B-mode EUS (FB-EUS). However, the diagnostic performance of Kupffer-phase imaging in contrast-enhanced harmonic EUS (CH-EUS) remains unclear. Hence, this study aimed to evaluate the usefulness of CH-EUS-based Kupffer-phase imaging for diagnosing liver metastasis from pancreatic cancer. METHODS: We retrospectively analyzed consecutive patients with pancreatic cancer who underwent contrast-enhanced CT (CE-CT) and FB-EUS, followed by CH-EUS, from 2011 to 2017. The diagnostic ability of CH-EUS against that of CE-CT and FB-EUS for metastasis in the left liver lobe was compared. Subsequently, the influences of CH-EUS on the determination of clinical stage and patient management for pancreatic cancer were assessed. RESULTS: We enrolled 426 patients with pancreatic cancer. Metastasis in the left liver lobe was present in 27.2% of patients. The diagnostic accuracy of CE-CT, FB-EUS, and CH-EUS was 90.6%, 93.4%, and 98.4%, respectively. The sensitivity and diagnostic accuracy of CH-EUS for metastasis in the left liver lobe were significantly higher than those of FB-EUS or CE-CT. The sensitivity of CH-EUS for detecting small liver metastasis (<10 mm) was considerably higher than that of CE-CT or FB-EUS (P < .001). In 2.1% of patients, only CH-EUS could detect a single distant metastasis of the left liver lobe, thereby upgrading the tumor staging and altering the clinical management. CONCLUSIONS: CH-EUS-based Kupffer-phase imaging increased the detectability of metastasis in the left liver lobe. This technique could be a reliable pretreatment imaging modality for clinical decision-making in patients with pancreatic cancer.

Utility of contrast-enhanced harmonic endoscopic ultrasonography for predicting the prognosis of pancreatic neuroendocrine neoplasms.

BACKGROUND AND AIMS: Pancreatic neuroendocrine neoplasms (PanNENs), including Grade 1 (G1) or G2 tumors, can have a poor prognosis. This study investigated the value of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) for predicting the prognosis of PanNENs. METHODS: This single-center, retrospective study included 47 consecutive patients who underwent CH-EUS and were diagnosed with PanNEN by surgical resection or EUS-guided fine needle aspiration between December 2011 and February 2016. Patients were divided into aggressive and non-aggressive groups according to the degree of clinical malignancy. CH-EUS was assessed regarding its capacity for diagnosing aggressive PanNEN, the correspondence between contrast patterns and pathological features, and its ability to predict the prognosis of PanNEN. RESULTS: There were 19 cases of aggressive PanNEN and 28 cases of non-aggressive PanNEN. The aggressive group included three G1, four G2, three G3 tumors, three mixed neuroendocrine non-neuroendocrine neoplasms, and six neuroendocrine carcinomas. CH-EUS was superior to contrast-enhanced computed tomography for the diagnosis of aggressive PanNEN (P < 0.001): hypo-enhancement on CH-EUS was an indicator of aggressive PanNEN, with sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 94.7%, 100%, 100%, 96.6%, and 97.9%, respectively. Among G1/G2 PanNENs, cases with hypo-enhancement on CH-EUS had a poorer prognosis than those with hyper/iso-enhancement (P = 0.0009). Assessment of 36 resected specimens showed that hypo-enhancement on CH-EUS was associated with smaller and fewer vessels and greater degree of fibrosis. CONCLUSION: Contrast-enhanced harmonic endoscopic ultrasonography may be useful for predicting the prognosis of PanNENs.

Efficacy of a modified double-guidewire technique using an uneven double lumen cannula (uneven method) in patients with surgically altered gastrointestinal anatomy (with video).

BACKGROUND: Balloon enteroscopy-assisted endoscopic retrograde cholangiopancreatography (BE-ERCP) has been reported to be effective for patients with surgically altered gastrointestinal anatomy. However, selective biliary cannulation remains difficult in BE-ERCP. We examined the usefulness of a modified double-guidewire technique using an uneven double lumen cannula (the uneven method) for BE-ERCP in patients with surgically altered gastrointestinal anatomy. METHODS: To clarify the usefulness of the uneven method for selective biliary cannulation in BE-ERCP in comparison to the pancreatic guidewire (PGW) method, 40 patients with surgically altered gastrointestinal anatomy who underwent BE-ERCP with successful placement of a guidewire in the pancreatic duct were evaluated. The uneven method was used in 18 cases (uneven group) and the PGW method was used in the remaining 22 cases (PGW group). RESULTS: The technical success rate of biliary cannulation was higher in the uneven group than in the PGW group (83.3 vs. 59.0%; P = 0.165). In addition, the time to biliary cannulation were significantly shorter in the uneven group than in the PGW group (6 vs. 18 min; P = 0.004; respectively). In the PGW group, post-ERCP pancreatitis (PEP) occurred in 3 of 22 cases (13.6%). No adverse events, including PEP, occurred in the uneven group. CONCLUSIONS: The uneven method may be a useful option of selective biliary cannulation in BE-ERCP for the patients with surgically altered gastrointestinal anatomy.

Value of additional endoscopic ultrasonography for surveillance after surgical removal of intraductal papillary mucinous neoplasms.

BACKGROUND AND AIM: This study evaluated the utility of endoscopic ultrasonography (EUS) combined with contrast-enhanced harmonic EUS (CH-EUS) for surveillance of the remnant pancreas after surgery for intraductal papillary mucinous neoplasm (IPMN). METHODS: This was a single-center, retrospective, descriptive study. A total of 134 consecutive patients who underwent surgical resection for IPMN between April 2009 and March 2015 were evaluated. Rates of recurrence and development of IPMN-concomitant pancreatic ductal adenocarcinoma (PDAC) during follow up were assessed. Clinical findings of patients with recurrence or development of PDAC were also evaluated. RESULTS: Of 134 resected IPMN 56 (41.8%) and 78 (58.2%) were classified as benign and malignant, respectively. Patients were followed up for a median of 29 months, 33 (24.6%) by both contrast-enhanced computed tomography (CE-CT) and EUS, and 101 (75.4%) by computed tomography (CT) alone. Thirteen patients (9.7%) showed tumor recurrence, five with intra-pancreatic recurrence and eight with extra-pancreatic metastases. An enhancing mural nodule within the dilated main pancreatic duct was successfully detected by EUS in one patient, but not by CE-CT. Two patients developed IPMN-concomitant PDAC during follow up. EUS combined with CH-EUS successfully detected small IPMN-concomitant PDAC in two patients, whereas these lesions were not detected by CT. CH-EUS was useful for better visualization of the margins of IPMN-concomitant PDAC in one of these two patients. CONCLUSION: Endoscopic ultrasonography combined with CH-EUS may improve follow up of patients with resected IPMN.

Primary Hepatic Adenosquamous Carcinoma Associated with Primary Sclerosing Cholangitis.

INTRODUCTION: Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disorder characterized by multiple fibrotic strictures of the bile duct. More than 40% of deaths in PSC patients are related to malignant tumors, including cholangiocarcinoma. Primary hepatic adenosquamous carcinoma (ASC) is a rare subtype of cholangiocarcinoma containing adenocarcinoma (AC) and squamous cell carcinoma (SCC) components, with a poorer prognosis than other cholangiocarcinomas. We report the first case of a hepatic ASC in a patient with PSC. CASE REPORT: A 28-year-old man was referred for diagnosis and treatment of a liver abscess suspected by contrast-enhanced computed tomography (CE-CT). He had a history of ulcerative colitis and PSC. Abdominal CE-CT revealed a 60-mm-diameter ring-shaped mass with central necrosis in the left lobe. Magnetic resonance imaging demonstrated a poorly circumscribed low-signal-intensity mass in T1-weighted imaging and a high-signal-intensity mass with a scattered low-signal-intensity area in T2-weighted imaging. Abdominal ultrasonography showed a hypoechoic component with a diffuse hyperechoic area in the tumor. Ultrasound-guided biopsy and histological examination showed tumor cells with both squamous and glandular differentiation. Left lobectomy was performed. Microscopic examination revealed 2 components, including moderately differentiated AC and well-differentiated SCC. The final diagnosis was hepatic ASC. CONCLUSION: This is the first reported case of hepatic ASC in a patient with PSC. Patients with PSC should be recognized as being at a risk of not only general cholangiocarcinoma, hepatocellular carcinoma, and metastatic liver tumor, but also ASC.

Detection of High-Grade Pancreatic Intraepithelial Neoplasia without Morphological Changes of the Main Pancreatic Duct over a Long Period: Importance for Close Follow-Up for Confirmation.

Pancreatic intraepithelial neoplasia (PanIN) is a microscopic papillary noninvasive lesion arising from the pancreatic ductal epithelium. However, the natural history and time to progression of high-grade PanIN remain unclear. Herein, we report 2 cases of high-grade PanIN without morphological changes of the main pancreatic duct (MPD) over relatively long periods. In the first case, a 63-year-old man was identified with MPD dilation. Magnetic resonance cholangiopancreatography showed localized stenosis in the pancreatic body with distal MPD dilation. Endoscopic retrograde pancreatography (ERP) was attempted because of possible high-grade PanIN but was unsuccessful. At 15-month follow-up, there was no change in the form of the MPD in various images. However, ERP was re-performed because of possible high-grade PanIN, and cytology showed adenocarcinoma. Postoperative pathology indicated diffuse lesions corresponding to high-grade PanINs in the MPD stenosis and surrounding branches. Final diagnosis was high-grade PanIN. In the second case, a 77-year-old man was identified with MPD dilation. Magnetic resonance cholangiography showed localized stenosis in the MPD of the pancreatic head with distal MPD dilation. He was diagnosed with MPD stenosis caused by chronic pancreatitis, and further examination was not recommended. At 25 months, the patient was referred to our hospital because of a mild change in MPD dilation. ERP showed localized irregular stenosis in the MPD, and cytology showed suspected adenocarcinoma. Postoperative pathology indicated a localized lesion with high-grade PanIN in the branch duct around the MPD stenosis. Final diagnosis was high-grade PanIN. In conclusion, we report 2 cases of high-grade PanIN without morphological changes of the MPD over relatively long periods. Even if a definite diagnosis is not obtained at initial examination, a strict follow-up observational study should be performed. Re-examination, including ERP, should also be considered in cases with risk factors of pancreatic cancer, even if there is no change in MPD form.

Association between the Risk Factors for Pancreatic Ductal Adenocarcinoma and Those for Malignant Intraductal Papillary Mucinous Neoplasm.

BACKGROUND AND AIMS: Risk factors for pancreatic ductal adenocarcinoma (PDAC) include diabetes mellitus, chronic pancreatitis, obesity, a family history of pancreatic cancer, and a history of smoking or alcohol consumption. The aim of this study was to evaluate the association between risk factors for PDAC and malignant intraductal papillary mucinous neoplasm (IPMN). METHODS: The study included 134 consecutive patients with IPMN who underwent surgical resection at Kindai University Hospital between April 2009 and March 2015. Data on the presence or absence of mural nodules (MNs) and risk factors for PDAC were evaluated. Multivariable logistic regression analysis was performed with malignant IPMN as the outcome variable and MNs and risk factors for PDAC as explanatory variables. RESULTS: The odds ratio of malignant IPMN to MNs was 3.88 (95% confidence interval [CI] 1.53-9.84; p = 0.004), whereas that of malignant IPMN to smoking history was 1.66 (95% CI 0.74-3.71; p = 0.22). When the presence of MNs was considered as a predictive factor for malignancy, the sensitivity and specificity were 88.5 and 32.1%, respectively, whereas when the presence of both smoking history and MNs was considered, the specificity improved to 73.2%, with a decrease in sensitivity to 42.3%. CONCLUSIONS: The presence of both a smoking history and MNs was a valuable predictive factor for malignant IPMN with high specificity. A smoking history should be considered before surgical resection in addition to the presence of MNs.

Drug-induced sarcoidosis-like reaction three months after BNT162b2 mRNA COVID-19 vaccination: A case report and review of literature.

BACKGROUND: A 70-year-old man with hepatitis C virus-related recurrent hepatocellular carcinoma was admitted for further diagnosis of a 1 cm iso-hyperechoic nodule in segment (S) 5. CASE SUMMARY: Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (EOB-MRI) revealed the nodule in S5 with a defect at the hepatobiliary phase, hyperintensity on diffusion weighted imaging (DWI) and hypointensity on apparent diffusion coefficient (ADC) map. Contrast-enhanced computed tomography revealed hypervascularity at the early phase, and delayed contrast-enhancement was observed at the late phase. Contrast-enhanced ultrasound (US) revealed incomplete defect at the late vascular phase. Inflammatory liver tumor, lymphoproliferative disease, intrahepatic cholangiocarcinoma (small duct type) and bile duct adenoma were suspected through the imaging studies. US guided biopsy, however, showed a noncaseating hepatic sarcoid-like epithelioid granuloma (HSEG), and histopathological analysis disclosed spindle shaped epithelioid cells harboring Langhans-type multinucleated giant cells. One month after admission, EOB-MRI signaled the disappearance of the defect at the hepatobiliary phase, of hyperintensity on DWI, of hypointensity on ADC map, and no stain at the early phase. CONCLUSION: That the patient had received BNT162b2 messenger RNA (mRNA) coronavirus disease 2019 vaccination 3 mo before the occurrence of HSEG, and that its disappearance was confirmed 4 mo after mRNA vaccination suggested that the drug-induced sarcoidosis-like reaction (DISR) might be induced by the mRNA vaccination. Fortunately, rechallenge of drug-induced DISR with the third mRNA vaccination was not confirmed.

Low-dose gemcitabine plus nab-paclitaxel versus standard-dose gemcitabine plus nab-paclitaxel in elderly patients with metastatic pancreatic cancer: A randomized Phase II trial.

Background and Aim: A multicenter, open-label randomized Phase II trial was conducted to determine whether low-dose gemcitabine plus nab-paclitaxel (GnP) could improve tolerability and show equivalent efficacy to the standard-dose GnP for elderly patients with metastatic pancreatic cancer. Methods: Consecutive patients aged ≥65 years with metastatic pancreatic cancer who presented at one of four Japanese referral centers between November 2016 and January 2021 were enrolled. The 60 patients were randomly assigned to low- or standard-dose groups with a 1:1 ratio. Patients in the low-dose GnP group received gemcitabine at a dose of 250 mg/m2 and nab-paclitaxel at 125 mg/m2. Results: Low-dose GnP significantly decreased the rate of cases requiring dose reduction (16.7% vs 63.3%). The response rate (36.7% vs 33.3%) and progression-free survival (7.3 vs 8 months) were comparable between the low- and standard-dose groups as determined by independent review. The difference in the median overall survival between the two groups was not significant (7.9 vs 12 months). The proportion of patients with hematologic and non-hematologic treatment-related adverse events was comparable between the two groups. Conclusion: Low-dose GnP had an equivalent efficacy to conventional therapy; however, it did not reduce adverse events.

Role of acylamino acid-releasing enzyme/oxidized protein hydrolase in sustaining homeostasis of the cytoplasmic antioxidative system.

Acylamino acid-releasing enzyme/oxidized protein hydrolase (AARE/OPH) has been biochemically demonstrated to be a bifunctional protease that has exopeptidase activity against Nα-acylated peptides and endopeptidase activity against oxidized and glycated proteins; however, its physiological role remains unknown. In this study, to determine its physiological significance, we produced AARE/OPH-overexpressing and -suppressed plants and assessed the biological impacts of AARE/OPH. The subcellular localization of Arabidopsis AARE/OPH was found to be cytoplasmic and nuclear by transient expression analysis of tdTomato-fused Arabidopsis AARE/OPH. Overexpression of AARE/OPH exhibited no apparent effect on the level of oxidized proteins because wild types probably have inherently high AARE/OPH activity. Through RNAi gene suppressing, we successfully produced AARE/OPH-suppressed Arabidopsis plants (aare) that exhibited almost no AARE activity. In the aare plant, electrolyte leakage by methyl viologen treatment was enhanced compared to that of non-transformant plants, suggesting that the plasma membranes of aare easily suffered oxidative damage, probably as a result of deterioration of the cytoplasmic antioxidative system. Correspondingly, proteomic analysis revealed that the aare plant accumulated a number of oxidized proteins including cytoplasmic antioxidant enzymes. On the basis of these results, we concluded that AARE/OPH plays a homeostatic role in sustaining the cytoplasmic antioxidative system.

Hepatitis B Virus Treatment and Hepatocellular Carcinoma: Controversies and Approaches to Consensus.

Background: Long-term therapy with nucleos(t)ide analogs (NAs) such as entecavir (ETV) and tenofovir disoproxil fumarate (TDF) favorably affects the incidence of hepatocellular carcinoma (HCC) on the basis of data from randomized or matched control studies. Recent data suggest a lower HCC incidence after 5 years of ETV or TDF therapy in chronic hepatitis B (CHB) patients, especially those with baseline cirrhosis. Summary: Three controversial issues remain to be resolved regarding hepatitis B virus (HBV) treatment and HCC. (1) The efficacy of antiviral treatment for the prevention of HCC is not established. The guidelines of the American Association for the Study of Liver Diseases (AASLD), the Asian Pacific Association for the Study of the Liver (APASL), and the European Association for the Study of the Liver (EASL) for the management of HBV infection state that antiviral treatment of HBV with interferon and NAs prevents the development of HCC. Among experts in CHB treatment, however, there is disagreement on the HCC prevention effects of antiviral treatment. (2) The rationale for antiviral management in patients with high HBV DNA and normal levels of alanine aminotransferase is unclear. The AASLD, EASL, and APASL guidelines do not recommend antiviral treatment for immune-tolerant CHB patients, and the terms and methods of treating such patients remain to be clarified. (3) The efficacy of first-line treatment with NAs, including ETV, TDF, and tenofovir alafenamide fumarate (TAF), to prevent HCC in CHB patients remains unknown. Several studies have produced controversial results regarding the effects of NAs on the risk and prevention of HCC. In the present review, we discuss these 3 issues, citing recent studies and clinical management guidelines from major international associations. Key Messages: Suggested approaches for reaching a consensus including applying the propensity score matching method, performing randomized controlled studies, and performing clinical studies with larger numbers of subjects and longer follow-up.

Prospective multicenter evaluation of moving cell metallic stents in endoscopic multiple stent deployment for hepatic hilar obstruction.

BACKGROUND AND AIM: Bilateral stent deployment for malignant biliary obstruction (MHBO) can be achieved using side-by-side (SBS) or stent-in-stent (SIS) procedures. Compared with SBS techniques, the procedural steps of SIS are technically complex due to the necessity of introducing the delivery system into a contralateral biliary tract through the mesh of the SEMS. To overcome this issue, a novel uncovered SEMS, the HILZO Moving Cell Stent (MCS) has been released. The present study examined the technical feasibility of treating MHBO using bilateral deployment of this novel stent without dilating the mesh of the first stent to achieve insertion of the second stent within a single session, using a prospective, multicenter setting. METHOD: The primary outcome in the present study was the technical success rate. Technical success was defined as deployment of bilateral MCSs into two or more biliary tracts using SIS without a dilation device in a single-session. RESULTS: A total of 27 patients with complications of MHBO were enrolled in this study. Bilateral SIS using two MCS was successfully performed in 23 patients without using dilation devices among 27 patients (initial technical success rate; 85.2%). Median time to recurrent biliary obstruction (TRBO) was 271 days. Stent dysfunction was observed in 12 patients (44.4%), and re-intervention was successfully performed in all patients without one patient who instead received best supportive care. CONCLUSIONS: The SIS technique using MCS without dilation of the mesh may be technically feasible and safe. In addition, this may be useful for re-intervention. Further comparative randomized trials are needed.