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Dive into the research topics where Wataru Onozato is active.

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Featured researches published by Wataru Onozato.


Surgery Today | 2009

Retrospective, matched case-control study comparing the oncologic outcomes between laparoscopic surgery and open surgery in patients with right-sided colon cancer

Takatoshi Nakamura; Wataru Onozato; Hiroyuki Mitomi; Masanori Naito; Takeo Sato; Heita Ozawa; Kazuhiko Hatate; Atsushi Ihara; Masahiko Watanabe

PurposeThe short- and long-term outcomes of laparoscopic surgery for right-sided colon cancer remain largely uninvestigated. This study was undertaken to compare the morbidity and mortality after either a laparoscopic right hemicolectomy (LRHC) or an open right hemicolectomy (ORHC) for this type of tumor.MethodsThe study group included 100 patients who underwent an LRHC and 100 patients who underwent an ORHC for right-sided colon cancer from 1990 through 2004. The two groups were retrospectively well matched with respect to sex, age (±5 years), and pathological tumor-node-metastasis (TNM) stage.ResultsThe median follow-up period was 83 months in the LRHC group and 105 months in the ORHC group. The LRHC group had a lower volume of intraoperative bleeding (P < 0.001), a lower rate of wound infection (P = 0.019) or postoperative intestinal obstruction (P = 0.013), and a shorter hospital stay (P < 0.001) than the ORHC group. The rate of recurrence did not differ significantly between the LRHC group (19%) and the ORHC group (22%). In patients with TNM stage I or II, the disease-free survival (DFS) rate (94.9% vs 95.1%) and overall survival (OS) rate (95.8% vs 95.0%) did not differ significantly between the two groups. A similar tendency was observed in patients with stage III with the rates for DFS (71.3% vs 60.4%) and OS (73.6% vs 64.1%), respectively.ConclusionsAn LRHC for right-sided colon cancer has the advantage over an ORHC of better short-term outcomes, and both groups have similar long-term oncologic outcomes. An LRHC is thus an acceptable alternative to an ORHC for the treatment of this type cancer.


Surgery Today | 2011

Successful laparoscopic resection of a sacrococcygeal teratoma in an adult: report of a case.

Atsuko Tsutsui; Takatoshi Nakamura; Hiroyuki Mitomi; Wataru Onozato; Takeo Sato; Heita Ozawa; Masanori Naito; Atsushi Ikeda; Atsushi Ihara; Masahiko Watanabe

Sacrococcygeal teratoma is a relatively rare congenital retroperitoneal tumor in adults. The standard treatment is a complete tumor resection. This report describes the successful laparoscopic resection of a sacrococcygeal teratoma. The patient was a 27-year-old woman with a well-demarcated cystic mass, 6 cm in diameter, in the retroperitoneum overlying the anterior surface of the sacrum. The mass was resected laparoscopically. A histopathological examination showed a mature teratoma. The magnifying function of the laparoscope allowed an en bloc resection in the narrow pelvic cavity, without damaging the tumor. The aesthetic outcome was excellent. The patient remains relapse-free at 1 year 6 months after surgery.


Journal of Surgical Oncology | 2011

Genetic alterations of K-ras may reflect prognosis in stage III colon cancer patients below 60 years of age.

Wataru Onozato; Keishi Yamashita; Kazuya Yamashita; Tatsuru Kuba; Hiroshi Katoh; Takatoshi Nakamura; Takeo Sato; Atsushi Ihara; Isao Okayasu; Masahiko Watanabe

Genetic alterations that are closely associated with patient prognosis can be landmarks of definitive therapeutic targets as well as useful biomarkers in human cancer clinics.


Surgery Today | 2007

Gastrointestinal Stromal Tumor of the Rectum Resected by Laparoscopic Surgery: Report of a Case

Takatoshi Nakamura; Atsushi Ihara; Hiroyuki Mitomi; Yukihito Kokuba; Takeo Sato; Heita Ozawa; Kazuhiko Hatade; Wataru Onozato; Masahiko Watanabe

A 53-year-old man visited our hospital with the chief complaint of pain on urination. On digital rectal examination, a rigid immobile tumor mass with a smooth surface was palpated on the anterior wall on the right side of the rectum near the anal canal. Computed tomography (CT) and magnetic resonance imaging (MRI) of the pelvis revealed a heterogeneous tumor mass measuring 6.5 cm in diameter, which occupied the cavity of the lesser pelvis. This rectal tumor was diagnosed to be a gastrointestinal stromal tumor (GIST) based on the results of a transrectal needle biopsy. A laparoscopic abdominoperineal resection of the rectum was performed to remove the mass. The intraoperative findings showed an ambiguous boundary between the tumor and the rectum but clear boundaries between the tumor and the peripheral organs, and the use of a laparoscope allowed for a good separation by providing a good visual field. The bleeding volume was approximately 80 ml and the operative time was 320 min. The macroscopic findings of excised specimens of the mass showed the tumor, measuring 6.5 × 5.5 × 5.0 cm, to be growing extrinsically from the anterior wall on the right side of the rectum. A histological examination of the excised specimens revealed at most 5 mitoses per 50 high-power fields (×400). The tumor mass was diagnosed to be a GIST of low-grade malignancy based on these findings. The postoperative course was favorable, and there were no postoperative complications. The patient was discharged on the 8th hospital day. Laparoscopic surgery is a minimally invasive surgical procedure for rectal GIST, which is excellent in terms of esthetics. Laparoscopic surgery is therefore considered to be useful for a resection of the rectum, because the magnifying effect allows surgical maneuvers with a favorable visual field within the pelvis.


Hepato-gastroenterology | 2011

Oncological outcomes of laparoscopic surgery in elderly patients with colon cancer: a comparison of patients 64 years or younger with those 75 years or older.

Takatoshi Nakamura; Hiroyuki Mitomi; Wataru Onozato; Takeo Sato; Atsushi Ikeda; Masanori Naito; Naoto Ogura; Hiroki Kamata; Akira Ooki; Masahiko Watanabe

BACKGROUND/AIMS We compared the results of laparoscopic resection of colon cancer between patients 75 years or older and those 64 years or younger, to confirm whether this procedure is warranted in elderly patients. METHODOLOGY The study group was comprised of patients with stage I to III colon cancer treated by laparoscopic surgery from 1995 through 2006. Oncologic outcomes were compared between 74 patients 75 years or older (elderly group) and 74 patients 64 years or younger (younger group) who were matched for gender, tumor location and pathological tumor-node-metastasis (TNM) stage. RESULTS In patients with stage I or II disease, the disease-free survival rate and overall survival rate were similar in the elderly group (100% and 100%, respectively) and the younger group (95.6% and 95.8%, respectively). In patients with stage III disease, the disease-free survival rate and overall survival rate were also similar in the elderly group (76.7% and 88.5%, respectively) and the younger group (88.5% and 88.5%, respectively). CONCLUSIONS Postoperative complications and long-term oncologic outcomes were similar in elderly patients and younger patients with colon cancer who underwent laparoscopic colectomy in our hospital. These results demonstrate that laparoscopic resection of colon cancer is warranted in patients 75 years or older.


Surgical Laparoscopy Endoscopy & Percutaneous Techniques | 2012

Benefits of a straight laparoscopic restorative proctocolectomy with ileal pouch anal anastomosis for ulcerative colitis: a retrospective case-matched study.

Heita Ozawa; Takatoshi Nakamura; Atsushi Ikeda; Masanori Naito; Takeo Sato; Wataru Onozato; Naoto Ogura; Masahiko Watanabe

Purposes: The aim of this study was to evaluate the benefit of straight laparoscopic restorative proctocolectomy (sLRP) with ileal pouch anal anastomosis for ulcerative colitis (UC). Methods: Twenty patients underwent sLRP or open restorative proctocolectomy. The 2 groups were retrospectively well matched with respect to sex, body mass index, and American Society of Anesthesiologists’ score. Results: The median operative time was longer in the sLRP group (P=0.0003). The median operative blood loss was significantly less in the sLRP group (P=0.0054). The median analgesic drug usage during the first 7 days after surgery was lower in the sLRP group (P=0.038). There were no differences in morbidity rates and long-term functional outcome measures between the groups. Conclusions: An sLRP for UC has the advantage over an open restorative proctocolectomy of better short-term outcomes, and both groups have similar long-term outcomes. This procedure is acceptable for minimally invasive surgery in patients with UC.


Hepato-gastroenterology | 2011

Short- and long-term outcomes of laparoscopic surgery in patients with pathological stage II and III colon cancer.

Takatoshi Nakamura; Hiroyuki Mitomi; Wataru Onozato; Takeo Sato; Atsushi Ikeda; Masanori Naito; Naoto Ogura; Hiroki Kamata; Akira Ooki; Masahiko Watanabe

BACKGROUND/AIMS In Japan, the safety and long-term outcomes of laparoscopic surgery for advanced colorectal cancer remains a matter of debate. We studied the safety and outcomes of laparoscopic surgery in patients with pathological stage II and III colon cancer. METHODOLOGY The study group comprised 253 patients with colon cancer who underwent laparoscopic surgery from January 1998 through December 2006. We studied surgical outcomes, invasiveness, safety, recurrence rates, recurrence patterns, and long-term outcomes. RESULTS Median follow-up was 67 months (range, 7-149). Laparoscopic surgery was converted to open surgery in 5 patients (2%). Postoperative complications occurred in 23 patients (9%); wound infections were most common (11 patients, 4.3%), followed by ileus (5 patients, 1.9%). Recurrence developed in 66 patients (26%). Liver and lung metastases were the most common types of recurrence; there was no port-site recurrence. The 10-year recurrence-free survival rate and the overall survival rate were respectively 92.9% and 93.3% in stage II disease, 82.7% and 82.9% in stage IIIA and IIIB disease, and 70.3% and 68.6% in stage IIIC disease. CONCLUSIONS In patients with pathological stage II and III colon cancer, laparoscopic surgery is safe, minimally invasive, and has good surgical outcomes, overall survival rates and recurrence-free survival rates. Our results suggest that laparoscopic surgery is a viable treatment option for pathological stage II and III colon cancer.


Asian Journal of Endoscopic Surgery | 2010

Minimally invasive straight laparoscopic total proctocolectomy for ulcerative colitis

Heita Ozawa; Yukihito Kokuba; Takatoshi Nakamura; Masanori Naito; Takeo Sato; Kazuhiko Hatate; Wataru Onozato; Hirohisa Miura; Atsuko Tsutsui; Atushi Ikeda; A. Ihara; Masahiko Watanabe

Introduction: We have performed straight laparoscopic total proctocolectomy for ulcerative colitis, in which all procedures, including transection of the rectum and anastomosis, were performed in the abdominal cavity. The primary objective of this study was to evaluate whether straight laparoscopic total proctocolectomy is technically feasible and safe.


World Journal of Surgery | 2008

Risk factors for wound infection after surgery for colorectal cancer.

Takatoshi Nakamura; Hiroyuki Mitomi; Atsushi Ihara; Wataru Onozato; Takeo Sato; Heita Ozawa; Kazuhiko Hatade; Masahiko Watanabe


Oncology Reports | 1994

Liver metastasis of colorectal cancer by protein-tyrosine phosphatase type 4A, 3 (PRL-3) is mediated through lymph node metastasis and elevated serum tumor markers such as CEA and CA19-9

Kazuhiko Hatate; Keishi Yamashita; Kazuya Hirai; Hiroshi Kumamoto; Takeo Sato; Heita Ozawa; Takatoshi Nakamura; Wataru Onozato; Yukihito Kokuba; Atsushi Ihara; Masahiko Watanabe

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Hiroyuki Mitomi

Dokkyo Medical University

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Yukihito Kokuba

Kyoto Prefectural University of Medicine

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