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Dive into the research topics where Masaki Kuwatani is active.

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Featured researches published by Masaki Kuwatani.


Journal of Hepato-biliary-pancreatic Sciences | 2014

Multicenter retrospective study of endoscopic ultrasound-guided biliary drainage for malignant biliary obstruction in Japan

Kazumichi Kawakubo; Hiroyuki Isayama; Hironari Kato; Takao Itoi; Hiroshi Kawakami; Keiji Hanada; Hirotoshi Ishiwatari; Ichiro Yasuda; Hirofumi Kawamoto; Fumihide Itokawa; Masaki Kuwatani; Tomohiro Iiboshi; Tsuyoshi Hayashi; Shinpei Doi; Yousuke Nakai

Endoscopic ultrasound‐guided biliary drainage (EUS‐BD) is considered to be an effective salvage procedure for failed endoscopic retrograde cholangiopancreatography in patients with unresectable malignant biliary obstruction. The aim of this retrospective study was to evaluate the efficacy and feasibility of EUS‐BD.


Gastrointestinal Endoscopy | 2013

Preliminary report on a new, fully covered, metal stent designed for the treatment of pancreatic fluid collections

Natsuyo Yamamoto; Hiroyuki Isayama; Hiroshi Kawakami; Naoki Sasahira; Tsuyoshi Hamada; Yukiko Ito; Naminatsu Takahara; Rie Uchino; Koji Miyabayashi; Suguru Mizuno; Hirofumi Kogure; Takashi Sasaki; Yousuke Nakai; Masaki Kuwatani; Kenji Hirano; Minoru Tada; Kazuhiko Koike

BACKGROUND Endoscopic transluminal treatment of pancreatic fluid collections (PFC) has been reported as an effective alternative approach to surgical treatment. A wide, short stent with an anti-migration system has been developed. OBJECTIVE To evaluate a newly developed, fully covered, self-expandable metal stent (FCSEMS) customized for cystogastrostomy. DESIGN Retrospective case series. SETTING Tertiary-care academic medical centers and affiliated hospitals. PATIENTS Nine patients who underwent endoscopic treatment of PFCs (5 with pseudocysts and 4 with walled-off pancreatic necrosis). INTERVENTION Stent deployment after endoscopic US-guided puncture. Irrigation and necrosectomy were performed at the discretion of the endoscopist. MAIN OUTCOME MEASUREMENTS Technical and clinical success rate, complications, and removability. RESULTS The FCSEMS was inserted successfully in all cases (9/9, 100%). Clinical success was achieved in 7 of 9 cases (77.8%). No early complications associated with the procedure were observed. Late complications were observed in 2 cases (bleeding and asymptomatic migration). The FCSEMS was removed without any complications in all 6 cases where it was attempted after the procedure had been completed (100%). LIMITATIONS This was a retrospective evaluation of a small number of cases. The FCSEMS was always inserted via the transgastric route. Follow-up duration was short. CONCLUSION The endoscopic approach that uses this new FCSEMS is feasible for the treatment of PFCs. However, further evaluation is required.


Journal of Gastroenterology and Hepatology | 2010

IgG4-related sclerosing cholangitis and autoimmune pancreatitis: histological assessment of biopsies from Vater's ampulla and the bile duct.

Hiroshi Kawakami; Yoh Zen; Masaki Kuwatani; Kazunori Eto; Shin Haba; Hiroaki Yamato; Keisuke Shinada; Kanako Kubota; Masahiro Asaka

Background and Aim:  Autoimmune pancreatitis is commonly associated with immunoglobulin (Ig) G4‐related sclerosing cholangitis (IgG4‐SC). The discrimination between IgG4‐SC and pancreatobiliary malignancies or primary sclerosing cholangitis (PSC) is now an important issue. The present study was carried out to examine the usefulness of endoscopic biopsies from Vaters ampulla and the bile duct to diagnose IgG4‐SC.


Endoscopy | 2009

Endoscopic retrograde cholangiography versus peroral cholangioscopy to evaluate intraepithelial tumor spread in biliary cancer

Hiroshi Kawakami; Masaki Kuwatani; Kazunori Etoh; Shin Haba; Hiroaki Yamato; Keisuke Shinada; Yoshitsugu Nakanishi; Eiichi Tanaka; Satoshi Hirano; Satoshi Kondo; Kanako Kubota; Masahiro Asaka

BACKGROUND AND STUDY AIMS Localized-type bile duct carcinoma (LBDC) is often accompanied by extensive intraepithelial tumor spread (ITS) of 2 cm or more, which makes radical resection more difficult. This retrospective case review compares the diagnostic accuracy of endoscopic retrograde cholangiography (ERC) and peroral cholangioscopy (POCS) to detect ITS beyond the visible LBDC. PATIENTS AND METHODS Forty-four consecutive patients with LBDC diagnosed between April 2004 and October 2008 who underwent radical resection with histopathological analysis were included in this study. Extensive ITS was found histopathologically in one-third of the cases (32 %). The outcome parameters were the presence or absence of extensive ITS and the extent of extensive ITS proximal and distal to the main tumor. RESULTS In six cases it was not possible to pass the cholangioscope through the tumor sites. ERC correctly identified the presence of extensive ITS in 11/14 cases and did not yield any false-positive results. The three cases in which ERC was negative were all correctly identified by POCS plus biopsy since the cholangioscope could be passed in all three cases. The extent of extensive ITS was correctly diagnosed by ERC alone, ERC with POCS, and ERC with POCS plus mapping biopsy in 22 %, 77 %, and 100 % of cases, respectively. CONCLUSIONS The presence of extensive ITS was correctly detected in 80 % of cases by ERC alone. POCS with mapping biopsy provided perfect diagnostic accuracy not only of the presence or absence but also of the extent of extensive ITS. However, POCS has the limitation that the cholangioscope cannot be passed through the tumor sites in approximately 15 % of cases.


Journal of Hepato-biliary-pancreatic Sciences | 2011

Preoperative biliary drainage for hilar cholangiocarcinoma: which stent should be selected?

Hiroshi Kawakami; Satoshi Kondo; Masaki Kuwatani; Hiroaki Yamato; Nobuyuki Ehira; Taiki Kudo; Kazunori Eto; Shin Haba; Joe Matsumoto; Kentaro Kato; Takahiro Tsuchikawa; Eiichi Tanaka; Satoshi Hirano; Masahiro Asaka

The controversy over whether and how to perform preoperative biliary drainage (PBD) in patients with hilar cholangiocarcinoma (HCA) remains unsettled. Arguments against PBD before pancreatoduodenectomy have recently been gaining momentum. However, the complication-related mortality rate is as high as 10% for patients with HCA who have undergone major liver resection, and liver failure is a major cause of postoperative death. This suggests the need for PBD to treat jaundice in HCA patients scheduled for major surgical resection of the liver and that major surgery should be performed only after the recovery of hepatic function. No definite criteria or guidelines outlining indications for PBD are currently available. In patients with HCA, PBD may be performed by either percutaneous transhepatic biliary drainage (PTBD) or endoscopic biliary drainage (EBD). No consensus, however, has been reached regarding which drainage method is more appropriate. No reported study has compared the effectiveness of PTBD, endoscopic biliary stenting (EBS), and endoscopic nasobiliary drainage (ENBD) in patients with HCA. This review summarizes the results of our study comparing the three methods and outlines the preoperative endoscopic management of segmental cholangitis (SC) in HCA patients undergoing PBD.


Endoscopy | 2015

Endoscopic ultrasound-guided choledochoduodenostomy vs. transpapillary stenting for distal biliary obstruction.

Kazumichi Kawakubo; Hiroshi Kawakami; Masaki Kuwatani; Yoshimasa Kubota; Shuhei Kawahata; Kimitoshi Kubo; Naoya Sakamoto

BACKGROUND AND STUDY AIMS Endoscopic ultrasound-guided choledochoduodenostomy (EUS-CDS) has gained popularity as an alternative to percutaneous biliary drainage for patients in whom endoscopic retrograde cholangiopancreatography has failed. There are no previous studies comparing EUS-CDS with endoscopic transpapillary stenting (ETS) as first-line treatment for distal malignant obstruction. The aim of this study was to compare the clinical efficacy and safety of EUS-CDS and ETS as first-line treatment in patients with distal malignant biliary obstruction. PATIENTS AND METHODS A total of 82 patients with distal malignant biliary obstruction underwent initial biliary drainage using self-expandable metal stents at a tertiary care university hospital. ETS was performed between June 2009 and May 2012, and EUS-CDS was performed between May 2012 and March 2014. Clinical success rates, adverse event rates, and reintervention rates were retrospectively evaluated for EUS-CDS and ETS. RESULTS A total of 26 patients underwent EUS-CDS and 56 underwent ETS. Clinical success rates were equivalent between the groups (EUS-CDS 96.2 %, ETS 98.2 %; P = 0.54). The mean procedure time was significantly shorter with EUS-CDS than with ETS (19.7 vs. 30.2 minutes; P < 0.01). The rate of overall adverse events was not significantly different between the groups (EUS-CDS 26.9 %, ETS 35.7 %; P = 0.46). Post-procedural pancreatitis was only observed in the ETS group (0 % vs. 16.1 %; P = 0.03). The reintervention rate at 1 year was 16.6 % and 13.6 % for EUS-CDS and ETS, respectively (P = 0.50). CONCLUSIONS EUS-CDS performed by expert endoscopists was associated with a short procedure time and no risk of pancreatitis, and would therefore be feasible as a first-line treatment for patients with distal malignant biliary obstruction.


British Journal of Cancer | 2013

Human equilibrative nucleoside transporter 1 and Notch3 can predict gemcitabine effects in patients with unresectable pancreatic cancer

Kazunori Eto; Hiroshi Kawakami; Masaki Kuwatani; Taiki Kudo; Yoko Abe; Shuhei Kawahata; Akira Takasawa; Midori Fukuoka; Yoshihiro Matsuno; Masahiro Asaka; Naoya Sakamoto

Background:Pancreatic ductal carcinoma (PDC) is one of the most lethal human carcinomas. Expression patterns of some genes may predict gemcitabine (GEM) treatment efficacy. We examined predictive indicators of survival in GEM-treated patients by quantifying the expression of several genes in pre-treatment endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) samples from patients with PDC.Methods:The expressions of human equilibrative nucleoside transporter 1 (hENT1), deoxycitidine kinase, ribonucleoside reductase 1, ribonucleoside reductase 2 and Notch3 in EUS-FNA tissue samples from 71 patients with unresectable PDC were quantified using real-time reverse transcription–polymerase chain reactions and examined for correlations with GEM sensitivity.Results:The log-rank test detected no significant differences in overall survival between GEM-treated patients with low and high mRNA levels of all genes examined. However, low Notch3 mRNA expression was significantly associated with longer overall survival in a multivariate analysis for survival (P=0.0094). High hENT1 expression level was significantly associated with a longer time to progression (P=0.039). Interaction tests for GEM administration and hENT1 or Notch3 mRNA expression were statistically significant (P=0.0054 and 0.0047, respectively).Conclusion:hENT1 and Notch3 mRNA expressions in EUS-FNA specimens were the key predictive biomarkers of GEM effect and GEM sensitivity in patients with unresectable PDC.


World Journal of Gastroenterology | 2011

Three cases of retroperitoneal schwannoma diagnosed by EUS-FNA.

Taiki Kudo; Hiroshi Kawakami; Masaki Kuwatani; Nobuyuki Ehira; Hiroaki Yamato; Kazunori Eto; Kanako Kubota; Masahiro Asaka

Schwannomas are peripheral nerve tumors that are typically solitary and benign. Their diagnosis is largely based on surgically resected specimens. Recently, a number of case reports have indicated that retroperitoneal schwannomas could be diagnosed with endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). We report the diagnosis of three cases of schwannoma using EUS-FNA. Subjects were two males and one female, ages 22, 40, and 46 years, respectively, all of whom were symptom-free. Imaging findings showed well-circumscribed round tumors. However, as the tumors could not be diagnosed using these findings alone, EUS-FNA was performed. Hematoxylin-eosin staining of the resulting tissue fragments revealed bland spindle cells with nuclear palisading. There was no disparity in nuclear sizes. Immunostaining revealed S-100 protein positivity and all cases were diagnosed as schwannomas. Ki-67 indexes were 3%-15%, 2%-3%, and 3%, respectively. No case showed any signs of malignancy. As most schwannomas are benign tumors and seldom become malignant, we observed these patients without therapy. All tumors demonstrated no enlargement and no change in characteristics. Schwannomas are almost always benign and can be observed following diagnosis by EUS-FNA.


World Journal of Gastroenterology | 2014

Influence of the safety and diagnostic accuracy of preoperative endoscopic ultrasound-guided fine-needle aspiration for resectable pancreatic cancer on clinical performance

Taiki Kudo; Hiroshi Kawakami; Masaki Kuwatani; Kazunori Eto; Shuhei Kawahata; Yoko Abe; Manabu Onodera; Nobuyuki Ehira; Hiroaki Yamato; Shin Haba; Kazumichi Kawakubo; Naoya Sakamoto

AIM To evaluate the safety and diagnostic accuracy of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) in a cohort of pancreatic cancer patients. METHODS Of 213 patients with pancreatic cancer evaluated between April 2007 and August 2011, 82 were thought to have resectable pancreatic cancer on the basis of cross-sectional imaging findings. Of these, 54 underwent EUS-FNA before surgery (FNA+ group) and 28 underwent surgery without preoperative EUS-FNA (FNA- group). RESULTS All 54 lesions were visible on EUS, and all 54 attempts at FNA were technically successful. The diagnostic accuracy according to cytology and histology findings was 98.1% (53/54) and 77.8% (42/54), respectively, and the total accuracy was 98.1% (53/54). One patient developed mild pancreatitis after EUS-FNA but was successfully treated by conservative therapy. No severe complications occurred after EUS-FNA. In the FNA+ and FNA- groups, the median relapse-free survival (RFS) was 742 and 265 d, respectively (P = 0.0099), and the median overall survival (OS) was 1042 and 557 d, respectively (P = 0.0071). RFS and OS were therefore not inferior in the FNA+ group. These data indicate that the use of EUS-FNA did not influence RFS or OS, nor did it increase the risk of peritoneal recurrence. CONCLUSION In patients with resectable pancreatic cancer, preoperative EUS-FNA is a safe and accurate diagnostic method.


Journal of Gastroenterology and Hepatology | 2016

Asian consensus statements on endoscopic management of walled-off necrosis Part 1: Epidemiology, diagnosis, and treatment.

Hiroyuki Isayama; Yousuke Nakai; Rungsun Rerknimitr; Christopher Jen Lock Khor; James Y. Lau; Hsiu-Po Wang; Dong Wan Seo; Thawee Ratanachu-ek; Sundeep Lakhtakia; Tiing Leong Ang; Shomei Ryozawa; Tsuyoshi Hayashi; Hiroshi Kawakami; N. Yamamoto; Takuji Iwashita; Fumihide Itokawa; Masaki Kuwatani; Masayuki Kitano; Keiji Hanada; Hirofumi Kogure; Tsuyoshi Hamada; Ryan Ponnudurai; Jong Ho Moon; Takao Itoi; Ichiro Yasuda; Atsushi Irisawa; Iruru Maetani

Walled‐off necrosis (WON) is a relatively new term for encapsulated necrotic tissue after severe acute pancreatitis. Various terminologies such as pseudocyst, necroma, pancreatic abscess, and infected necrosis were previously used in the literature, resulting in confusion. The current and past terminologies must be reconciled to meaningfully interpret past data. Recently, endoscopic necrosectomy was introduced as a treatment option and is now preferred over surgical necrosectomy when the expertise is available. However, high‐quality evidence is still lacking, and there is no standard management strategy for WON. The consensus meeting aimed to clarify the diagnostic criteria for WON and the role of endoscopic interventions in its management. In the Consensus Conference, 27 experts from eight Asian countries took an active role and examined key clinical aspects of WON diagnosis and endoscopic management. Statements were crafted based on literature review and expert opinion, employing the modified Delphi method. All statements were substantiated by the level of evidence and the strength of the recommendation. We created 27 consensus statements for WON diagnosis and management, including details of endoscopic procedures. When there was not enough solid evidence to support the statements, this was clearly acknowledged to facilitate future research. Proposed management strategies were formulated and are illustrated using flow charts. These recommendations, which are based on the best current scientific evidence and expert opinion, will be useful for guiding endoscopic management of WON. Part 1 of this statement focused on the epidemiology, diagnosis, and timing of intervention.

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