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Dive into the research topics where Ken Ohnita is active.

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Featured researches published by Ken Ohnita.


Gastrointestinal Endoscopy | 2011

Usefulness of oral prednisolone in the treatment of esophageal stricture after endoscopic submucosal dissection for superficial esophageal squamous cell carcinoma

Naoyuki Yamaguchi; Hajime Isomoto; Toshiyuki Nakayama; Tomayoshi Hayashi; Hitoshi Nishiyama; Ken Ohnita; Fuminao Takeshima; Saburo Shikuwa; Shigeru Kohno; Kazuhiko Nakao

BACKGROUND Endoscopic submucosal dissection (ESD) permits en bloc removal of superficial esophageal squamous cell carcinoma. However, postprocedure stricture is common after ESD for extensive tumors, and multiple endoscopic balloon dilation (EBD) is required for recalcitrant cases. OBJECTIVE To evaluate the effectiveness of oral prednisolone in controlling postprocedure esophageal stricture. DESIGN Retrospective study. SETTING Endoscopy department at a university hospital. PATIENTS Patients who underwent complete circular or semicircular ESD for esophageal squamous cell carcinoma involving more than three fourths of the lumen were treated with either pre-emptive EBD or oral prednisolone. INTERVENTION Preemptive EBD was started on the third day post-ESD and continued twice weekly for 8 weeks. Oral prednisolone was started at 30 mg/day on the third day post-ESD , tapered gradually, and then discontinued 8 weeks later. An additional EBD was performed on demand in both groups whenever dysphagia appeared. MAIN OUTCOME MEASUREMENT The incidence of esophageal stricture and number of EBD sessions required to relieve dysphagia. RESULTS Stricture at 3 months after ESD was found in 7 of 22 patients in the preemptive EBD group but only 1 of 19 in the oral prednisolone group (P < .05). The average number of EBD sessions required was 15.6 in the preemptive EBD group and 1.7 in the oral prednisolone group (P < .0001). After complete circular ESD, 32.7 EBD sessions were needed on average in the preemptive EBD group, whereas fewer were needed in the oral prednisolone group (P < .05). LIMITATIONS Nonrandomized study. CONCLUSIONS Post-ESD esophageal strictures were persistent even if treated preemptively with multiple EBD sessions, but oral prednisolone may offer a useful preventive option.


Scandinavian Journal of Gastroenterology | 2004

Ghrelin enhances gastric motility through direct stimulation of intrinsic neural pathways and capsaicin-sensitive afferent neurones in rats

H. Fukuda; Y. Mizuta; Hajime Isomoto; F. Takeshima; Ken Ohnita; Kazuo Ohba; Katsuhisa Omagari; Kohtaro Taniyama; Shigeru Kohno

Background: Ghrelin may stimulate gastric motility via the vagal nerve pathway. However, the mechanism of ghrelin-induced changes in gastrointestinal motility has not yet been clearly defined. The present study was designed to investigate whether ghrelin accelerates gastric emptying via capsaicin-sensitive afferent neurones and directly affects the enteric neuromuscular function. Methods: Gastric emptying of nutrient solids was assessed after intravenous administration of saline or ghrelin in conscious rats. The effects of ghrelin on gastric emptying were also examined in rats pretreated with capsaicin. Gastric emptying and intestinal transit of non-caloric liquids were evaluated using [Formula: See Text]Cr solution. The effects of ghrelin on spontaneous contractile activities of isolated strips from stomach and jejunum were also investigated and the influence of ghrelin on motor responses to carbachol and electrical field stimulation was examined. Results: Ghrelin significantly accelerated gastric emptying of both nutrient solids and non-caloric liquids in conscious rats. The intestinal transit of non-caloric liquids was also enhanced by ghrelin. Pretreatment with capsaicin prevented the ghrelin-induced acceleration of gastric emptying of nutrient solids. Ghrelin did not modulate spontaneous and carbachol-induced contractions of strips of gastric body, gastric antrum and jejunum. However, electrical field stimulation-induced contractions were significantly enhanced by ghrelin in the gastric body. Conclusions: The results suggest that the stimulatory effects of ghrelin on gastric motility are mediated by direct stimulation of the enteric neural pathway and capsaicin-sensitive afferent neurones.


Endoscopy | 2009

Clinicopathological factors associated with clinical outcomes of endoscopic submucosal dissection for colorectal epithelial neoplasms

Hajime Isomoto; H. Nishiyama; Naoyuki Yamaguchi; E. Fukuda; H. Ishii; K. Ikeda; Ken Ohnita; Kazuhiko Nakao; Shigeru Kohno; Saburo Shikuwa

BACKGROUND AND STUDY AIMS Endoscopic submucosal dissection (ESD) permits removal of colorectal epithelial neoplasms en bloc, but a substantial risk of procedure-related perforation has been reported. We sought to unravel the clinicopathological factors associated with the clinical outcomes of ESD for colorectal epithelial neoplasms in a large series. PATIENTS AND METHODS ESD was done in 278 patients with 292 colorectal tumors that fulfilled the inclusion criteria. The criteria for ESD were: lesion greater than 20 mm in size, lesion with fibrotic scarring, locally residual colorectal lesion, or invasive carcinoma with slight submucosal penetration. Resection was assessed as en bloc or piecemeal, complete (en bloc with tumor-free lateral and basal margins) or incomplete. Complications including perforation and bleeding were assessed, and factors related to each were analyzed using logistic regression. Patients underwent multiple follow-up endoscopic examinations (mean 4.6; median 4; range 2 - 9; total number 1010). RESULTS En bloc resection was achieved in 90.1 % of lesions (263/292) and resection was deemed to be complete in 233 (79.8 %). Right-side colonic location and the finding of fibrosis were the significant contributors to incomplete resection. Perforation was seen in 24 cases (8.2 %), and was associated with large tumor size and the presence of fibrosis. When the contributive factors for each were combined, the risks of incomplete resection and perforation were substantially increased. CONCLUSION The present study provides useful information for predicting risks for incomplete resection and complication in colorectal ESD.


The American Journal of Gastroenterology | 2005

Impact of Helicobacter pylori infection on gastric and plasma ghrelin dynamics in humans.

Hajime Isomoto; Hiroaki Ueno; Vladimir Saenko; Muhtashan S. Mondal; Yoshito Nishi; Naoko Kawano; Ken Ohnita; Yohei Mizuta; Akira Ohtsuru; Shunichi Yamashita; Masamitsu Nakazato; Shigeru Kohno

OBJECTIVES:There are contradictory reports on the relationship between Helicobacter pylori and circulating ghrelin. We sought to clarify the influence of H. pylori infection on gastric and plasma ghrelin dynamics in humans.METHODS:Using endoscopic biopsies from the corpus of 56 H. pylori-infected patients and 25 uninfected subjects, ghrelin mRNA expression levels and gastric ghrelin peptide contents were measured by real-time polymerase chain reaction and radioimmunoassay, respectively. We also measured plasma ghrelin concentrations and analyzed the numbers of ghrelin immunoreactive cells in the fundic gland area. Fifty-one patients with H. pylori infection were treated with a 7-day triple therapy consisting of lansoprazole, clarithromycin, and amoxicillin.RESULTS:The gastric ghrelin mRNA expression level of H. pylori-positive patients (1.64 ± 1.27 in arbitrary units) was significantly lower than in H. pylori-negative subjects (4.87 ± 4.1, p < 0.0001). A similar trend was noted for ghrelin peptide contents (31.2 ± 27.5 vs 81.2 ± 64.1 ng/mg protein, respectively, p < 0.0001). There was no significant difference in the number of ghrelin immunoreactive cells/mm2 in terms of H. plyori status. Plasma ghrelin concentrations in H. pylori-infected patients (144.6 ± 7.8.8 fmol/ml) were significantly lower than in uninfected subjects (196.1 ± 97.2, p < 0.05) and increased following cure of the infection. Plasma ghrelin levels correlated positively with the expression levels of ghrelin mRNA (r = 0.583, p < 0.0001) and peptide products (r = 0.574, p < 0.0001). There was a significant stepwise decrease in gastric ghrelin mRNA expression (p < 0.05), peptide contents (p < 0.01) and density of ghrelin immunoreactive cells (p < 0.05) with progression of histological severity of glandular atrophy in the corpus. The histological severity of chronic inflammation also negatively influenced the ghrelin mRNA expression (p < 0.001) and peptide production (p < 0.005).CONCLUSIONS:H. pylori infection has a negative impact on gastric and plasma ghrelin dynamics. Chronic inflammatory and atrophic changes associated with the infection may affect gastric ghrelin biosynthesis and contribute to the low circulating levels.


Digestion | 2009

Clinical outcomes of endoscopic submucosal dissection for early gastric cancer by indication criteria.

Naoyuki Yamaguchi; Hajime Isomoto; Eiichiro Fukuda; Kohki Ikeda; Hitoshi Nishiyama; Motohisa Akiyama; Eisuke Ozawa; Ken Ohnita; Tomayoshi Hayashi; Kazuhiko Nakao; Shigeru Kohno; Saburo Shikuwa

Background and Study Aims: Endoscopic submucosal dissection (ESD) can remove early gastric cancer (EGC) en bloc. We sought to assess the feasibility and efficacy of ESD and the clinical outcomes based on the indication criteria. Patients and Methods: 551 patients with 589 EGC lesions were divided into the guideline criteria group (elevated lesion ≤20 mm in diameter and depressed lesion ≤10 mm without ulceration) and the expanded criteria group (mucosal cancer without ulcer findings irrespective of tumor size; mucosal cancer with ulcer findings ≤3 cm in diameter; and minute submucosal invasive cancer ≤3 cm in size). Results: En bloc, complete and curative resection were achieved in 98.6 and 93.0, 95.1 and 88.5, and 97.1 and 91.1%, for the guideline and expanded criteria lesions, respectively; the differences between the 2 groups were significant for each. The expanded criteria lesions were at significantly higher risk of ESD-associated bleeding and perforation. Overall survival was adequate irrespective of the indications, and the disease-specific survival rates were 100% in both. Conclusion: ESD for EGCs that met the expanded criteria was acceptable, though the resection rates and safety were decreased compared to those for the guideline criteria lesions.


Digestive Endoscopy | 2014

Peroral endoscopic myotomy for esophageal achalasia: Clinical impact of 28 cases

Hitomi Minami; Hajime Isomoto; Naoyuki Yamaguchi; Kayoko Matsushima; Yuko Akazawa; Ken Ohnita; Fuminao Takeshima; Haruhiro Inoue; Kazuhiko Nakao

The aim of the present study was to clarify the efficacy of peroral endoscopic myotomy (POEM) for esophageal achalasia.


BMC Gastroenterology | 2011

Management of esophageal stricture after complete circular endoscopic submucosal dissection for superficial esophageal squamous cell carcinoma

Hajime Isomoto; Naoyuki Yamaguchi; Toshiyuki Nakayama; Tomayoshi Hayashi; Hitoshi Nishiyama; Ken Ohnita; Fuminao Takeshima; Saburo Shikuwa; Shigeru Kohno; Kazuhiko Nakao

BackgroundEndoscopic submucosal dissection (ESD) permits removal of esophageal epithelial neoplasms en bloc, but is associated with esophageal stenosis, particularly when ESD involves the entire circumference of the esophageal lumen. We examined the effectiveness of systemic steroid administration for control of postprocedural esophageal stricture after complete circular ESD.MethodsSeven patients who underwent wholly circumferential ESD for superficially extended esophageal squamous cell carcinoma were enrolled in this study. In 3 patients, prophylactic endoscopic balloon dilatation (EBD) was started on the third post-ESD day and was performed twice a week for 8 weeks. In 4 patients, oral prednisolone was started with 30 mg daily on the third post-ESD day, tapered gradually (daily 30, 30, 25, 25, 20, 15, 10, 5 mg for 7 days each), and then discontinued at 8 weeks. EBD was used as needed whenever patients complained of dysphagia.ResultsEn bloc ESD with tumor-free margins was safely achieved in all cases. Patients in the prophylactic EBD group required a mean of 32.7 EBD sessions; the postprocedural stricture was dilated up to 18 mm in diameter in these patients. On the other hand, systemic steroid administration substantially reduced or eliminated the need for EBD. Corticosteroid therapy was not associated with any adverse events. Post-ESD esophageal stricture after complete circular ESD was persistent, requiring multiple EBD sessions.ConclusionsUse of oral prednisolone administration may be an effective treatment strategy for reducing post-ESD esophageal stricture after complete circular ESD.


European Journal of Gastroenterology & Hepatology | 2010

Clinical outcomes of endoscopic submucosal dissection in elderly patients with early gastric cancer.

Hajime Isomoto; Ken Ohnita; Naoyuki Yamaguchi; Eiichiro Fukuda; Kohki Ikeda; Hitoshi Nishiyama; Motohisa Akiyama; Eisuke Ozawa; Kazuhiko Nakao; Shigeru Kohno; Saburo Shikuwa

Objectives Endoscopic submucosal dissection (ESD) has advantages over conventional endoscopic mucosa resection. The number of elderly patients (more than 75 years old) with early gastric cancer (EGC) has been steadily increasing. We sought to assess clinical outcomes of ESD for EGC in elderly. Methods ESD was performed for patients with EGC, who fulfilled the criteria for ESD: mucosal cancer without ulcer findings irrespective of tumor size; mucosal cancer with ulcer findings 3 cm or less in diameter; and minute submucosal invasive cancer 3 cm or less in size. Two hundred and sixty elderly patients (≥75 years old) with 279 lesions, and 401 non-elderly patients with 434 lesions were enrolled to this study. The patients underwent ESD and then received periodic endoscopic follow-up and metastatic surveys for 6–89 months (median: 30 months). Resectability (en-bloc or piecemeal resection), curability (curative or noncurative resection), completeness (complete or incomplete resection), complications, and survival rates were assessed. Rersults The one-piece resection rate was significantly lower in elderly patients (93.9%) than in non-elderly patients (97.9%). The complete resection rate was significantly lower in elderly patients (87.4%) than in non-elderly patients (96.6%). Pneumonia, but not bleeding or perforation, developed in association with ESD more frequently in the elderly patients by 2.2%. Local tumor recurrence was quite rare, and the overall and disease-free survival rates were acceptable irrespective of age. Conclusion En-bloc and complete resections were achieved less frequently in elderly patients, but the long-term outcomes in elderly EGC patients may be excellent, and ESD is a feasible treatment in the elderly.


Digestive Diseases and Sciences | 2005

Circulating ghrelin levels in patients with various upper gastrointestinal diseases.

Hajime Isomoto; Hiroaki Ueno; Yoshito Nishi; Toru Yasutake; Kenji Tanaka; Naoko Kawano; Ken Ohnita; Yohei Mizuta; Kenichiro Inoue; Masamitsu Nakazato; Shigeru Kohno

The stomach is the main source of circulating ghrelin. Plasma concentrations of this hormone in patients with various upper gastrointestinal diseases remain undetermined. Thus we measured plasma ghrelin levels by radioimmunoassay in 225 subjects, including 134 Helicobacter pylori-infected and 91 uninfected subjects. They included 67 patients with chronic gastritis (CG), 26 with benign gastric polyp (BGP), 24 with gastric ulcer (GU), 24 with reflux esophagitis (RE), 18 with duodenal ulcer (DU), 28 with acute gastritis (AG), 23 with gastric cancer (GC), and 39 who had normal mucosa on upper endoscopy (N). Plasma pepsinogen I and II levels were also measured. The extent of gastritis was assessed endoscopically. Ghrelin levels differed significantly among the different disease groups. Plasma ghrelin concentrations were lowest in the CG group, followed by the GU group, and highest in the AG patients. There was a significant difference in the levels between differentiated and undifferentiated GC. Ghrelin concentrations in BGP, RE, and DU patients were comparable to those in the N group. Ghrelin circulating levels were lower in H. pylori-positive than –negative individuals, but the significant differences among disease groups were still observed in H. pylori-infected and uninfected populations. Ghrelin concentrations correlated positively with plasma pepsinogen I levels and I/II ratios and inversely with the extent of H. pylori-related gastritis. Plasma ghrelin levels varied widely in diverse conditions of the upper digestive tract, reflecting the inflammatory and atrophic events of the background gastric mucosa. Further investigation is warranted to unravel the mechanisms of the high circulating ghrelin levels in certain upper gastrointestinal diseases.


Journal of Clinical Gastroenterology | 2007

Relation among plasma ghrelin level, gastric emptying, and psychologic condition in patients with functional dyspepsia.

Ken-ichi Takamori; Yohei Mizuta; Fuminao Takeshima; Yuko Akazawa; Hajime Isomoto; Ken Ohnita; Kazuo Ohba; Katsuhisa Omagari; Saburo Shikuwa; Shigeru Kohno

Background and Goals Neurohormonal factors might play a role in the pathogenesis of functional dyspepsia (FD). However, the role of ghrelin, a gastrointestinal hormone that stimulates gastric motility, in FD is not yet clearly defined. The present study was designed to investigate plasma ghrelin levels and their relation with gastric emptying and psychologic status in FD. Methods Sixteen patients with FD of the dysmotility type and 19 healthy controls were enrolled in the study. Plasma active and desacyl ghrelin concentrations before and after test meal were measured by enzyme-linked immunosorbent assay. Gastric emptying and psychologic condition were studied using 13C acetate breath test and questionnaires, respectively. Results Gastric emptying was significantly prolonged in patients with FD compared with controls. Fasting desacyl and total ghrelin levels were significantly lower in FD patients than in controls, but fasting active ghrelin levels and postprandial levels of ghrelin in both forms were similar between the 2 groups. Fasting total ghrelin levels in FD patients did not differ from the postprandial levels, in contrast to what was found for controls. There was no significant association among gastric emptying, plasma ghrelin levels, and psychologic factors in FD patients. Conclusions Total secretory ability or metabolic condition of ghrelin may be altered in patients with FD. This seems to play a role in the pathophysiology of dysmotility type FD, independent of delayed gastric emptying or psychologic disorders.

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