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Dive into the research topics where Masanao Nakamura is active.

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Featured researches published by Masanao Nakamura.


Gastrointestinal Endoscopy | 2005

Endoscopic resection of Peutz-Jeghers polyps throughout the small intestine at double-balloon enteroscopy without laparotomy

Naoki Ohmiya; Ayumu Taguchi; Kennosuke Shirai; Nobuyuki Mabuchi; Daigo Arakawa; Hironobu Kanazawa; Masayasu Ozeki; Masahiro Yamada; Masanao Nakamura; Akihiro Itoh; Yoshiki Hirooka; Yasumasa Niwa; Tetsuro Nagasaka; Masafumi Ito; Shinji Ohashi; Shozo Okamura; Hidemi Goto

BACKGROUND Small-bowel enteroscopy with the double-balloon method was developed to improve access to the small intestine. This study evaluated the usefulness of this method for the resection of small-intestinal Peutz-Jeghers polyps. METHODS Two patients with Peutz-Jeghers syndrome underwent nonsurgical double-balloon enteroscopic resection of polyps throughout the small intestine. OBSERVATIONS Multiple polyps in the jejunum were successfully resected via the oral route, as were the polyps in the ileum via the anal route. All 18 polyps (10-60 mm in size) were resected without subsequent bleeding or perforation. Histopathologically, 3 large polyps (>30 mm diameter) were hamartomas with adenomatous components. CONCLUSIONS Double-balloon enteroscopy was safe and useful for the diagnosis and the treatment of Peutz-Jeghers polyps throughout the small intestine. Double-balloon enteroscopic polypectomy might preclude complications of Peutz-Jeghers syndrome, including intussusception, bleeding, and tumorogenesis, thereby obviating the need for multiple laparotomies.


Gastrointestinal Endoscopy | 2009

Outcome after enteroscopy for patients with obscure GI bleeding : diagnostic comparison between double-balloon endoscopy and videocapsule endoscopy

Daigo Arakawa; Naoki Ohmiya; Masanao Nakamura; Wataru Honda; Osamu Shirai; Akihiro Itoh; Yoshiki Hirooka; Yasumasa Niwa; Osamu Maeda; Takafumi Ando; Hidemi Goto

BACKGROUND Double-balloon endoscopy (DBE) and videocapsule endoscopy (VCE) have been useful in managing obscure GI bleeding (OGIB). OBJECTIVE This study compared diagnostic yields of OGIB between DBE and VCE, and evaluated the outcome after DBE. DESIGN A single-center retrospective study. SETTING A tertiary-referral hospital. PATIENTS Between June 2003 and February 2007, 162 consecutive patients with OGIB were enrolled and treated. The diagnostic yield between VCE and DBE was compared in 74 patients. MAIN OUTCOME MEASUREMENTS Comparison of diagnostic yields between DBE and VCE, and the prognosis after DBE. RESULTS Of 162 patients, 95 (59%) were diagnosed with small-bowel diseases. They were treated by medical, enteroscopic, and surgical therapies (n = 35, 30, and 30, respectively). A comparison of the overall diagnostic yield between DBE (64%) and VCE (54%) was not significantly different. The 4 VCE-positive DBE-negative cases were because of inaccessibility of DBE. The 11 VCE-negative DBE-positive cases were because of a failure to detect lesions in the proximal small bowel and the Roux-en-Y loop, and because of diverticula. At a median follow-up of 555 days after DBE, 11 patients with small-bowel diseases developed rebleeding; all were treated by enteroscopic or medical therapies. Vascular diseases, comorbidities, especially portal hypertensive disease and chronic renal failure that required hemodialysis, and severe anemia (Hb </=7.0 g/dL) were associated with rebleeding. LIMITATIONS A retrospective comparative study, and participation bias. CONCLUSIONS A complementary combination between DBE and VCE was useful for the management of OGIB. In particular, patients with vascular disease, comorbidities, and severe anemia should be intensively treated.


Gastrointestinal Endoscopy | 2009

Small-bowel obstruction: diagnostic comparison between double-balloon endoscopy and fluoroscopic enteroclysis, and the outcome of enteroscopic treatment.

Naoki Ohmiya; Daigo Arakawa; Masanao Nakamura; Wataru Honda; Osamu Shirai; Ayumu Taguchi; Akihiro Itoh; Yoshiki Hirooka; Yasumasa Niwa; Osamu Maeda; Takafumi Ando; Hidemi Goto

BACKGROUND Small-bowel obstruction (SBO) sometimes remains undiagnosed and untreatable without surgery. OBJECTIVE To evaluate the diagnostic yields of SBO between double-balloon endoscopy (DBE) and fluoroscopic enteroclysis (FE), and the outcome of enteroscopic treatment. DESIGN Single-center, retrospective, and prospective study. SETTING Tertiary-referral hospital. PATIENTS Between June 2003 and July 2007, 66 consecutive patients with SBO were enrolled, investigated, and treated. MAIN OUTCOME MEASUREMENTS A comparison of diagnostic yields between DBE and FE, and the prognosis after enteroscopic balloon dilation. RESULTS The diagnostic yield of DBE for SBO (95%) was higher than that of FE (71%) in 59 patients who underwent both examinations (P= .004). The first treatment included 27 surgical, 25 enteroscopic, and 14 conservative therapies. Of 47 enteroscopic balloon dilation procedures in 22 patients, 45 (96%) were successful. Of 16 patients with Crohns disease, 11 (69%) remained asymptomatic over the postdilation follow-up period but 5 relapsed: 2 recovered by repeated dilations, but 3 required surgery. Of 6 patients who had diseases other than Crohns disease, 4 (67%) remained asymptomatic but 2 relapsed: one with remission of metastasis recovered by repeated dilations, and one with ischemic enteritis required surgery. Anastomotic stricture was an independent marker of the symptom-free outcome (hazard ratio 0.037-0.084, P= .037). Two acute pancreatitis, one perforation, and one exacerbation of SBO complications occurred. LIMITATIONS Small sample size and participation bias. CONCLUSIONS DBE was useful for the diagnosis of SBO. Balloon dilation is considered an alternative to surgery in patients with fibrotic strictures both related and unrelated to Crohns disease.


Journal of Gastroenterology | 2008

Efficacy of rebamipide for diclofenac-induced small-intestinal mucosal injuries in healthy subjects : a prospective, randomized, double-blinded, placebo-controlled, cross-over study

Yasumasa Niwa; Masanao Nakamura; Naoki Ohmiya; Osamu Maeda; Takafumi Ando; Akihiro Itoh; Yoshiki Hirooka; Hidemi Goto

BackgroundAlthough obscure gastrointestinal bleeding cannot be detected by colonoscopy or upper endoscopy, wireless video capsule endoscopy (VCE) is capable of imaging it. Few data are available on medical therapy for patients with nonsteroidal anti-inflammatory drug (NSAID)-induced small-intestinal mucosal injuries. The aim of this study was to compare prevention by rebamipide and placebo of NSAID-induced smallintestinal injury in healthy subjects.MethodsTen healthy subjects who provided written informed consent were enrolled. Rebamipide or placebo plus diclofenac was administered with omeprazole for 7 days, and for an additional 7-day period with treatments reversed in the same subjects, with a 4-week washout period between treatments. VCE of the small intestine was performed four times, before and after each of the two study periods.ResultsThe number of subjects with small-intestinal mucosal injuries was higher in the placebo group (8/10) than in the rebamipide group (2/10) (P = 0.023). Two cases of ulcer and one of bleeding were observed in the placebo group, while no ulcer or bleeding was observed in the rebamipide group.ConclusionsRebamipide had significantly higher efficacy than placebo in preventing NSAID-induced small-intestinal mucosal injury.


Pancreas | 2012

Malignant transformation of branch duct-type intraductal papillary mucinous neoplasms of the pancreas based on contrast-enhanced endoscopic ultrasonography morphological changes: focus on malignant transformation of intraductal papillary mucinous neoplasm itself.

Eizaburo Ohno; Akihiro Itoh; Hiroki Kawashima; Takuya Ishikawa; Hiroshi Matsubara; Yuya Itoh; Yosuke Nakamura; Takeshi Hiramatsu; Masanao Nakamura; Ryoji Miyahara; Naoki Ohmiya; Masatoshi Ishigami; Yoshiaki Katano; Hidemi Goto; Yoshiki Hirooka

Objectives The natural history of branch duct–type intraductal papillary mucinous neoplasms (BD-IPMNs) of the pancreas remains unclear. We conducted a retrospective long-term follow-up study for malignant transformation (MT) of BD-IPMNs focusing on morphological changes. Methods The subjects consisted of 142 patients who underwent contrast-enhanced endoscopic ultrasonography for initial diagnosis from January 2001 with more than 12 months of follow-up. The MT rate, including the co-occurrence of invasive ductal cancer, was evaluated by univariate and multivariate analysis. In addition, on the basis of morphological changes in patients who underwent surgery, the predictive factors for malignant IPMNs were evaluated. Results Median follow-up term was 42.5 months (range, 12–105 months). Thirty patients who exhibited morphological changes underwent surgery. Malignant transformation occurred in 9 patients (6.3%), and 5-year MT rate was 10.7%. The co-occurrence of invasive ductal cancer was seen in 5 patients. Multivariate analysis showed that the existence of mural nodules at initial diagnosis and involvement of main pancreatic duct were significant predictors of MT of BD-IPMN. Conclusions Malignant transformation of BD-IPMN is not rare. The observation of morphological changes of main pancreatic duct and nodules, mainly on contrast-enhanced endoscopic ultrasonography, is practical and useful for predicting MT of BD-IPMN itself. Abbreviations IPMN - intraductal papillary mucinous neoplasm BD-IPMN - branch duct–type intraductal papillary mucinous neoplasm MT - malignant transformation IDC - invasive ductal cancer MPD - main pancreatic duct CE-EUS - contrast-enhanced endoscopic ultrasonography EUS-FNA - endoscopic ultrasonography–guided fine needle aspiration MD-IPMN - main duct–type intraductal papillary mucinous neoplasm MD-CT - multidetector row computed tomography HR - hazard ratio OR - odds ratio


Cancer Science | 2011

Primary gastrointestinal follicular lymphoma involving the duodenal second portion is a distinct entity: A multicenter, retrospective analysis in Japan

Katsuyoshi Takata; Hiroyuki Okada; Naoki Ohmiya; Shotaro Nakamura; Yasuhiko Kitadai; Akira Tari; Taiji Akamatsu; Hiroki Kawai; Shu Tanaka; Hiroshi Araki; Takashi Yoshida; Hirokazu Okumura; Hogara Nishisaki; Tamotsu Sagawa; Norihiko Watanabe; Nobuyoshi Arima; Noritaka Takatsu; Masanao Nakamura; Shunichi Yanai; Hiroyasu Kaya; Toshiaki Morito; Yasuharu Sato; Hisataka Moriwaki; Choitsu Sakamoto; Yasumasa Niwa; Hidemi Goto; Tsutomu Chiba; Takayuki Matsumoto; Daisuke Ennishi; Tomohiro Kinoshita

We conducted a multicenter, retrospective study to determine the anatomical distribution and prognostic factors of gastrointestinal (GI) follicular lymphoma (FL). This study included 125 patients with stage I and II1 GI–FL. Of the 125 patients, the small intestine was examined in 70 patients, with double‐balloon endoscopy and/or capsule endoscopy. The most frequently involved GI–FL site was the duodenal second portion (DSP) (81%), followed by the jejunum (40%); 85% of patients with involvement of the DSP also had jejunal or ileal lesions. The absence of abdominal symptoms and macroscopic appearance of multiple nodules were significantly present in the DSP‐positive group. During a median follow up of 40 months, six patients showed disease progression. Patients with involvement of the DSP had better progression‐free survival (PFS) than those without such involvement (P = 0.001). A multivariate analysis revealed that male sex, the presence of abdominal symptoms, and negative involvement of the DSP were independently associated with poor PFS. In conclusion, most patients with GI–FL have duodenal lesions associated with multiple jejunal or ileal lesions. Gastrointestinal follicular lymphomas involving the DSP might be a distinct entity showing a favorable clinical course. (Cancer Sci 2011; 102: 1532–1536)


Pancreas | 2011

Dynamic quantitative evaluation of contrast-enhanced endoscopic ultrasonography in the diagnosis of pancreatic diseases

Hiroshi Matsubara; Akihiro Itoh; Hiroki Kawashima; Toshifumi Kasugai; Eizaburo Ohno; Takuya Ishikawa; Yuya Itoh; Yosuke Nakamura; Takeshi Hiramatsu; Masanao Nakamura; Ryoji Miyahara; Naoki Ohmiya; Masatoshi Ishigami; Yoshiaki Katano; Hidemi Goto; Yoshiki Hirooka

Objectives: This study aimed to investigate the usefulness of contrast-enhanced endoscopic ultrasonography (EUS) with time-intensity curve (TIC) in differentiating pancreatic diseases. Methods: Patients who underwent contrast-enhanced EUS between January 2007 and June 2009 were analyzed retrospectively, including 48 with pancreatic ductal cancer (PC), 14 with autoimmune pancreatitis (AIP), 13 with mass-forming pancreatitis (MFP), and 16 with pancreatic endocrine tumor (PET). After intravenous injection of contrast agent, contrast imaging pattern, TIC-based quantitative evaluation, and diagnostic ability of EUS in combination with TIC to diagnose benignancy or malignancy were assessed. Results: Hypovascular and heterogeneous pattern (42/48) in PC, isovascular and homogenous (21/27) in AIP and MFP, and hypervascular and rapid stained (16/16) in PET were observed. The echo intensity reduction rate from the peak at 1 minute was the greatest in PC followed by MFP, AIP, and PET (P < 0.05). The diagnostic accuracies based on contrast imaging pattern (84.0%) and TIC (88.0%) were higher than those based on B-mode imaging (82.6%) and dynamic computed tomography (81.3%). In EUS in combination with TIC, sensitivity, specificity, and accuracy rose up to 95.8%, 92.6%, and 94.7%, respectively. Conclusions: Contrast-enhanced EUS with the dynamic quantitative analysis preparing TIC increased the diagnostic accuracy for pancreatic diseases.


Gastrointestinal Endoscopy | 2010

Management of small-bowel polyps in Peutz-Jeghers syndrome by using enteroclysis, double-balloon enteroscopy, and videocapsule endoscopy

Naoki Ohmiya; Masanao Nakamura; Hiroyuki Takenaka; Kenji Morishima; Takeshi Yamamura; Makoto Ishihara; Ryoji Miyahara; Hiroki Kawashima; Akihiro Itoh; Yoshiki Hirooka; Osamu Watanabe; Takafumi Ando; Hidemi Goto

BACKGROUND Management of small-bowel polyps in Peutz-Jeghers syndrome (PJS) by using fluoroscopic enteroclysis (FE), double-balloon enteroscopy (DBE), and videocapsule enteroscopy (VCE) remains incompletely determined. OBJECTIVE To evaluate the usefulness of FE, VCE, and DBE and compute the polyp growth rate. DESIGN Single-center retrospective study. SETTING Tertiary referral hospital. PATIENTS Between June 2003 and January 2010, 18 consecutive patients with PJS were enrolled. MAIN OUTCOME MEASUREMENTS Polyp detection rates among FE, VCE, and DBE, histology of resected polyps, and the polyp growth rate. RESULTS Total enteroscopy rate was higher at VCE (89%) than at DBE (52%; 27% in patients with ≥2 previous laparotomies and 90% in patients with ≤1 [P = .001]). FE demonstrated fewer polyps than DBE, whereas VCE had detection rates similar to those of DBE. Of 387 DBE-resected and 22 surgically resected polyps, histologic analysis of 110 retrieved polyps showed adenoma or adenocarcinoma in 30.0% of polyps >20 mm and in only 1.3% of polyps ≤20 mm (P < .0001). Multiple linear regression analysis showed that the number of small-bowel polyps >10 mm (X1; P = .0366) and colorectal polyps >5 mm (X2; P = .002) were independent predictors of the growth rate of small-bowel polyps (Y), and a forward stepwise selection model was constructed: Y = 0.136 × X1 + 0.289 × X2 - 0.589 (R(2) = 0.665). LIMITATIONS Small sample size. CONCLUSIONS DBE and VCE were useful for the management of small-bowel polyps in PJS. VCE may replace barium examinations for surveillance after polyp resection at intervals depending on the polyp growth rate.


Clinical Gastroenterology and Hepatology | 2009

Diagnosis of Pancreatic Disorders Using Contrast-Enhanced Endoscopic Ultrasonography and Endoscopic Elastography

Yoshiki Hirooka; Akihiro Itoh; Hiroki Kawashima; Eizaburo Ohno; Takuya Ishikawa; Hiroshi Matsubara; Yuya Itoh; Masanao Nakamura; Ryoji Miyahara; Naoki Ohmiya; Yasumasa Niwa; Masatoshi Ishigami; Yoshiaki Katano; Hidemi Goto

Contrast-enhanced endoscopic ultrasonography (CE-EUS) and EUS-elastography are cutting-edge diagnostic modalities for pancreatic disorders. Each pancreatic disorder has characteristic hemodynamics. CE-EUS uses color Doppler flow imaging to classify pancreatic lesions into a spectrum of solid and cystic patterns. Although there is overlap in the patterns generated by specific types of tumors, some types of tumors tend to produce distinct flow images. EUS-elastography can assess tissue hardness by measuring its elasticity. This parameter appears to correlate with the malignant potential of the lesions. Tissue elasticity studies can provide information on both its pattern and distribution. The former is the conventional method of morphologic diagnosis, but it is restricted to observations made in a region of interest. The latter is an unbiased analysis that can be performed by image analysis software and is theoretically constant, regardless of regions of interest. The evolving modalities of CE-EUS and EUS-elastography might provide clinical utility in the diagnosis of pancreatic disorders.


Gastrointestinal Endoscopy | 2012

Enteroscopic and radiologic diagnoses, treatment, and prognoses of small-bowel tumors.

Wataru Honda; Naoki Ohmiya; Yoshiki Hirooka; Masanao Nakamura; Ryoji Miyahara; Eizaburo Ohno; Hiroki Kawashima; Akihiro Itoh; Osamu Watanabe; Takafumi Ando; Hidemi Goto

BACKGROUND Small-bowel tumors (SBTs) represent a diagnostic challenge. OBJECTIVE To evaluate the usefulness of contrast-enhanced CT (CECT), fluoroscopic enteroclysis (FE), videocapsule endoscopy (VCE), and double-balloon endoscopy (DBE) and the outcome after treatment. DESIGN Single-center, retrospective study. SETTING Tertiary-care referral hospital. PATIENTS Between June 2003 and May 2011, 159 consecutive patients with SBTs (93 malignant and 66 benign) were enrolled. MAIN OUTCOME MEASUREMENTS Comparison of diagnostic yields among CECT, FE, VCE, and DBE and the prognosis. RESULTS CECT and FE had significantly lower diagnostic yields of SBTs ≤ 10 mm, but VCE and DBE had high yields of SBTs regardless of size. CECT had a significantly lower diagnostic yield of epithelial tumors compared with subepithelial tumors. When stratified by the site, the diagnostic yield of VCE for SBTs located only in the distal duodenum/the proximal jejunum (73%) was significantly lower than that for SBTs located in other areas (90%). Comparisons among the 4 methods revealed that VCE and DBE had significantly higher diagnostic yields than CECT, and DBE had significantly higher diagnostic yields than VCE, but a combination of CECT and VCE had a diagnostic yield similar to that of DBE. The histologic diagnostic yield of SBTs by DBE was 92%, and 25% of SBTs were enteroscopically treated. Metastatic tumors had the poorest overall survival, followed by adenocarcinomas and malignant lymphomas. LIMITATIONS Retrospective comparative study. CONCLUSION For the detection of SBTs, a combination screening method by using VCE and CECT is recommended. DBE is useful for histologic diagnosis and endoscopic treatment.

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