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Dive into the research topics where Hiroki Imagawa is active.

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Featured researches published by Hiroki Imagawa.


Digestive Endoscopy | 2011

RISK FACTORS FOR BLEEDING AFTER ENDOSCOPIC SUBMUCOSAL DISSECTION OF GASTRIC EPITHELIAL NEOPLASM

Makoto Higashiyama; Shiro Oka; Shinji Tanaka; Yoji Sanomura; Hiroki Imagawa; Takayoshi Shishido; Shigeto Yoshida; Kazuaki Chayama

Background:  Although endoscopic submucosal dissection (ESD) is standard therapy in Japan for gastric epithelial neoplasm, the complication rate is unsatisfactory, with postoperative bleeding as the major complication. The aim of the present study was to determine risk factors for post‐ESD bleeding in patients with gastric epithelial neoplasm.


Gastrointestinal Endoscopy | 2011

Improved visibility of lesions of the small intestine via capsule endoscopy with computed virtual chromoendoscopy

Hiroki Imagawa; Shiro Oka; Shinji Tanaka; Ikue Noda; Makoto Higashiyama; Youji Sanomura; Takayoshi Shishido; Shigeto Yoshida; Kazuaki Chayama

BACKGROUND We can now enhance video capsule endoscopy (CE) images in real time by means of a flexible spectral imaging color enhancement (FICE) digital processing system. Reports on the clinical usefulness of this system are few. OBJECTIVE To clarify whether visualization of lesions of the small intestine is improved by FICE image analysis. DESIGN A retrospective study. SETTING Academic medical center. METHODS Five physicians compared FICE images with corresponding conventional images of 145 lesions obtained from 122 patients who underwent video CE at our hospital. The lesions were classified as angioectasia (n=23), erosion/ulceration (n=45), or tumor (n=75), and 3 different sets of FICE images were viewed (ie, at 3 different wavelength settings). Physicians rated the visibility of the lesions on FICE images as follows: +2 (improved visibility), +1 (somewhat improved visibility), 0 (visibility equivalent to that of conventional video CE visibility), -1 (somewhat decreased visibility), and -2 (decreased visibility). Scores for each lesion were totaled (per FICE setting) and evaluated. Intraobserver agreement was also examined. RESULTS With FICE setting 1 (red 595 nm, green 540 nm, blue 535 nm), improvement was achieved for 87% (20/23) of angioectasia images, 53.3% (26/47) of erosion/ulceration images, and 25.3% (19/75) of tumor images. With setting 2 (red 420 nm, green, 520 nm, blue 530 nm), improvement was achieved for 87% (20/23), 25.5% (12/47), and 20.0% (15/75), respectively. With setting 3, only equivalence was achieved. Intraobserver agreement was good to satisfactory at 5.4 or higher. LIMITATIONS Single-center study. CONCLUSIONS CE-FICE improves visibility of small-bowel angioectasia, erosion/ulceration, and tumor.


Hepato-gastroenterology | 2012

Diagnostic yield of capsule endoscopy vs. double-balloon endoscopy for patients who have undergone total enteroscopy with obscure gastrointestinal bleeding.

Takayoshi Shishido; Shiro Oka; Shinji Tanaka; Taiki Aoyama; Ikue Watari; Hiroki Imagawa; Shigeto Yoshida; Kazuaki Chayama

BACKGROUND/AIMS The usefulness of capsule endoscopy (CE) and of double-balloon endoscopy (DBE) for detection of small-bowel lesions is widely accepted. We compared CE- and DBE-based detection of small-bowel lesions in patients with obscure gastrointestinal bleeding (OGIB) who underwent total enteroscopy by both CE and DBE. METHODOLOGY One hundred eighteen consecutive patients (70 men, 48 women; mean age 62.9±18.4 years) with OGIB underwent both CE and DBE. CE was performed and DBE was then performed within 1 week by both retrograde and antegrade approaches. Differences in detection rates were analyzed. RESULTS Overall, small-bowel lesions were detected by CE in 53 patients (44.9%) and by DBE in 63 patients (53.4%) (p=0.01); agreement between CE and DBE findings was good (kappa statistic=0.76). Total enteroscopy was achieved by both modalities in 54 patients; CE detected small-bowel lesions in 25 of these patients (46.3%), and DBE detected lesions in 28 of these patients (51.9%) (p=0.25); agreement between CE and DBE findings was very good (kappa statistic=0.88). CONCLUSIONS Our data support preferential use of noninvasive CE for patients with OGIB and subsequent DBE examination in most cases.


Scandinavian Journal of Gastroenterology | 2011

Improved detectability of small-bowel lesions via capsule endoscopy with computed virtual chromoendoscopy: A pilot study

Hiroki Imagawa; Shiro Oka; Shinji Tanaka; Ikue Noda; Makoto Higashiyama; Youji Sanomura; Takayoshi Shishido; Shigeto Yoshida; Kazuaki Chayama

Abstract Objective. Real-time video capsule endoscopy (CE) with flexible spectral imaging color enhancement (FICE) improves visibility of small-bowel lesions. This article aims to clarify whether CE-FICE also improves detectability of small-bowel lesions. Patients and methods. A total of 55 patients who underwent CE at Hiroshima University Hospital during the period November 2009 through March 2010 were enrolled in the study. Five patients were excluded from the study because residues and transit delays prevented sufficient evaluation. Thus, 50 patients participated. Two experienced endoscopists (each having interpreted more than 50 capsule videos) analyzed the images. One interpreted conventional capsule videos; the other, blinded to interpretation of the conventional images, interpreted CE-FICE images obtained at settings 1–3 (setting 1: red 595 nm, green 540 nm, blue 535 nm; setting 2: red 420 nm, green 520 nm, blue 530 nm; setting 3: red 595 nm, green 570 nm, blue 415 nm). Lesions were classified as angioectasia, erosion, ulceration, or tumor. Detectability was compared between the two modalities. Time taken to interpret the capsule videos was also determined. Results. Seventeen angioectasias were identified by conventional CE; 48 were detected by CE-FICE at setting 1, 45 at setting 2, and 24 at setting 3, with significant differences at settings 1 and 2 (p = 0.0003, p < 0.0001, respectively). Detection of erosion, ulceration, and tumor did not differ statistically between conventional CE and CE-FICE, nor did interpretation time (conventional CE 36 ± 6.9 min; CE-FICE setting 1, 36 ± 6.4 min; setting 2, 38 ± 5.8 min; setting 3, 35 ± 6.7 min). Conclusions. CE-FICE is superior in the lesion detection in comparison with conventional CE and improves detection of angioectasia.


BMC Gastroenterology | 2013

Effectiveness of polaprezinc for low-dose aspirin-induced small-bowel mucosal injuries as evaluated by capsule endoscopy: a pilot randomized controlled study

Ikue Watari; Shiro Oka; Shinji Tanaka; Taiki Aoyama; Hiroki Imagawa; Takayoshi Shishido; Shigeto Yoshida; Kazuaki Chayama

BackgroundTreatment of low-dose aspirin (LDA)-induced small-bowel injury has not been established. Polaprezinc, a chelate of zinc and L-carnosine, may be efficacious for such injury. We conducted a pilot randomized controlled study to investigate whether polaprezinc is effective against LDA-induced small-bowel injuries.MethodsConsecutive patients under long-term (>3 months) LDA treatment and who agreed to participate in our study underwent initial capsule endoscopy (CE). Patients with LDA-induced small-bowel injury apparent upon initial CE (n = 20) were randomized into a polaprezinc (150 mg/day for 4 weeks) group and a control (no polaprezinc treatment) group. All underwent follow-up CE after 4 weeks. Changes in the number and characteristics of small-bowel mucosal injuries were compared within and between the two groups.ResultsThe median number of reddened lesions and erosions/ulcers upon follow-up CE in the polaprezinc group significantly decreased (P < 0.05). However, there was no significant difference in the median number of reddened lesions and erosions/ulcers upon follow-up CE in the control group.ConclusionsCo-administration of polaprezinc may be effective against small-bowel mucosal injury associated with long-term LDA therapy.Trial registrationUMIN Clinical Trials Registry UMIN000003687.


World Journal of Gastroenterology | 2012

Outcome of patients who have undergone total enteroscopy for obscure gastrointestinal bleeding.

Takayoshi Shishido; Shiro Oka; Shinji Tanaka; Hiroki Imagawa; Yoshito Takemura; Shigeto Yoshida; Kazuaki Chayama

AIM To assess the diagnostic success and outcome among patients with obscure gastrointestinal bleeding who underwent total enteroscopy with double-balloon endoscopy. METHODS Total enteroscopy was attempted in 156 patients between August 2003 and June 2008 at Hiroshima University Hospital and achieved in 75 (48.1%). It is assessed whether sources of bleeding were identified, treatment methods, complications, and 1-year outcomes (including re-bleeding) after treatment, and we compared re-bleeding rates among patients. RESULTS The source of small bowel bleeding was identified in 36 (48.0%) of the 75 total enteroscopy patients; the source was outside the small bowel in 11 patients (14.7%) and not identified in 28 patients (37.3%). Sixty-one of the 75 patients were followed up for more than 1 year (27.2 ± 13.3 mo). Four (6.6%) of these patients showed signs of re-bleeding during the first year, but bleeding did not recur after treatment. Although statistical significance was not reached, a marked difference was found in the re-bleeding rate between patients in whom total enteroscopy findings were positive (8.6%, 3/35) and negative (3.8%, 1/26) (3/35 vs 1/26, P = 0.63). CONCLUSION A good outcome can be expected for patients who undergo total enteroscopy and receive proper treatment for the source of bleeding in the small bowel.


Scandinavian Journal of Gastroenterology | 2009

Usefulness and limitations of transabdominal ultrasonography for detecting small-bowel tumors

Akira Fukumoto; Shinji Tanaka; Hiroki Imagawa; Takayoshi Shishido; Shiro Oka; Shigeto Yoshida; Hiroyasu Yamada; Kazuaki Chayama

Objective. New methods of examining the small bowel, e.g. capsule endoscopy (CE) and double-balloon endoscopy (DBE), have recently been developed. Transabdominal ultrasonography (TUS) is a conventional, non-invasive, and less-expensive modality. The aim of this study was to evaluate the usefulness and limitations of TUS for the detection of small-bowel tumors. Material and methods. A total of 371 patients who underwent CE and/or DBE were enrolled in the study. All patients underwent TUS prior to CE and DBE. We evaluated the sensitivity and specificity of TUS in detecting small-bowel tumors, diagnosis and size of tumors, overall detection rate of tumors by TUS, detection rate according to tumor size and shape, and the ultrasonographic features of the tumors. Results. The sensitivity and specificity rates of TUS were 26.4% and 98.6%, respectively. A total of 92 tumors detected by CE and/or DBE were analyzed. Mean size of small-bowel tumors was 20.0 mm. The detection rate of TUS was 25.0%; the detection rate for tumors smaller than 20 mm was only 1.8%, while that for tumors of 20 mm or larger was 59.5%. Despite the tumor size being 20 mm or larger, none of the granular lateral spreading lesions were detected by TUS, but all of the circumferential ulcerative lesions could be detected using this procedure. Conclusions. TUS is considered to be a useful modality for detecting small-bowel lesions of large volume. We consider that TUS is the first choice modality for examining small-bowel lesions because it is a non-invasive and non-expensive procedure that can detect large lesions.


Endoscopy | 2017

Endoscopic submucosal dissection of early colorectal neoplasms with a monopolar scissor-type knife: short- to long-term outcomes

Toshio Kuwai; Toshiki Yamaguchi; Hiroki Imagawa; Yuki Sumida; Takeshi Takasago; Yuki Miyasako; Tomoyuki Nishimura; Sumio Iio; Atsushi Yamaguchi; Hirotaka Kouno; Hiroshi Kohno; Sauid Ishaq

Background and study aims Endoscopic submucosal dissection (ESD) for colorectal neoplasms remains challenging because of technical issues imposed by the complex anatomical features of the large intestine. We evaluated the feasibility, and the short- and long-term clinical outcomes of ESD for early colorectal neoplasms performed using the Stag-beetle Knife Jr. (SB Knife Jr.) Patients and methods We retrospectively assessed 228 patients who underwent ESD for 247 colorectal lesions with the SB Knife Jr. Clinicopathological characteristics of the neoplasms, complications, and various short- and long-term outcomes were evaluated. Results Mean tumor size was 34.3 mm and median procedure time was 76 minutes. The SB Knife Jr. achieved 98.4 % en bloc resection, 93.9 % complete resection, and 85.4 % curative resection. No perforations occurred during the procedure, and a delayed bleeding rate of 2.4 % was observed. Long-term outcomes were favorable with no distant recurrence, 1.1 % local recurrence, a 5-year overall survival rate of 94.1 % and 5-year tumor-specific survival rate of 98.6 % in patients with cancer. Conclusions ESD using the SB Knife Jr. is technically efficient and safe in treating early colorectal neoplasms and is associated with favorable short- and long-term outcomes.


Digestive Endoscopy | 2013

Feasibility of spiral enteroscopy in Japanese patients: study in two tertiary hospitals.

Atsuo Yamada; Hirotsugu Watabe; Shiro Oka; Hirofumi Kogure; Hiroki Imagawa; Yuka Kobayashi; Hirobumi Suzuki; Ikue Watari; Taiki Aoyama; Hiroyuki Isayama; Yutaka Yamaji; Mitsuhiro Fujishiro; Shinji Tanaka; Kazuhiko Koike

Despite recent advances in enteroscopy, such as balloon enteroscopy, accessing the small intestine remains challenging. Spiral enteroscopy is a novel technique in which an endoscope is fitted with a rotating overtube that has a soft spiral fin at the tip. Whereas spiral enteroscopy is beginning to be carried out in Western countries, it is not common in many Asian countries. The aim of the present study was to evaluate the efficacy and safety of spiral enteroscopy in Japanese patients.


Endoscopy | 2017

Endoscopic full-thickness resection for inverted Meckel’s diverticulum using double-balloon enteroscopy

Kazutoshi Konomatsu; Toshio Kuwai; Toshiki Yamaguchi; Hiroki Imagawa; Atsushi Yamaguchi; Hirotaka Kouno; Hiroshi Kohno

Meckel’s diverticulum contains all layers of the small bowel wall and is usually treated by surgery [1, 2]. Inverted Meckel’s diverticulum is rare, with only two reports of endoscopic resection [3, 4]. As preoperative diagnosis of an inverted Meckel’s diverticulum is difficult [5], it was not diagnosed prior to resection in either case, and consequently perforation due to endoscopic resection was reported in one case [3]. In the current case, we diagnosed the condition preoperatively, and subsequently used two detachable snares prior to resection to prevent hemorrhage or perforation. We then safely treated the inverted Meckel’s diverticulum using endoscopic full-thickness resection with double-balloon enteroscopy (DBE). A 78-year-old man was admitted to our institution because of anemia and a positive fecal occult blood test. Abdominal ultrasound identified a hypoechoic polypoid lesion, with a hyperechoic head (▶Video1). A contrasted abdominal computed tomography scan also identified an elongated pedunculated polypoid lesion, with fat tissue in its center, in the distal ileum (▶Video1). Capsule endoscopy demonstrated a submucosal tumor-like lesion (▶Video1), and selective contrast-enhanced radiography indicated an elongated intraluminal polypoid lesion that was approximately 8 cm in size (▶Video1). Retrograde DBE indicated that the polypoid lesion exhibited intestinal villous mucosa on the surface at the head and typical mucosal features at the stalk of the antimesenteric attachment (▶Fig. 1). This indicated that the lesion was an inverted Meckel’s diverticulum, and endoscopic full-thickness resection with DBE was attempted. First, the stem of the polyp was closed with two detachable snares before resection to prevent hemorrhage or perforation. Then, conventional polypectomy with DBE was performed. The resection surface was closed with four clips after the polypectomy (▶Fig. 2, ▶Video1). Histopathological analysis revealed an 80×10mm inverted Meckel’s diverticulum without ectopic tissue (▶Video1). The patient was discharged 2 days later without adverse events. Endoscopy_UCTN_Code_TTT_1AP_2AD

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Shinji Tanaka

Tokyo Medical and Dental University

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