Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Y. Hamashima is active.

Publication


Featured researches published by Y. Hamashima.


Abdominal Imaging | 1997

Portal vein aneurysm: report of six cases and review of the literature

Y. Ohnami; Hideaki Ishida; K. Konno; H. Naganuma; Y. Hamashima; A. Zeniya; Osamu Masamune

Abstract. Portal vein aneurysm is very rare, and its relation to portal hypertension has been emphasized. We report six cases of portal vein aneurysm (five extrahepatic and one intrahepatic). All patients were asymptomatic and had no signs suggestive of portal hypertension; the lesion was incidentally detected by ultrasound. Color Doppler sonography showed a constant hepatopetal flow along the aneurysmal wall, which immediately led to the diagnosis. We stress the usefulness of color Doppler sonography for studying the hemodynamics of this vascular anomaly and briefly review the literature.


Abdominal Imaging | 1999

Splenic lymphangioma : US and CT diagnosis and clinical manifestations

Tomoya Komatsuda; Hideaki Ishida; K. Konno; Y. Hamashima; H. Naganuma; M. Sato; J. Ishida; Osamu Masamune

AbstractBackground and methods: We tried to determine the role and problems of gray-scale sonography (US), computed tomography (CT), and color Doppler sonography in the diagnosis of splenic lymphangioma on the basis of our experience with seven adult cases with this relatively rare tumor. Results: (1) The whole spleen was replaced by a collection of cysts of different sizes with or without calcifications in six patients. In these patients, color Doppler sonography showed the intrasplenic arteries and veins running along the cyst walls. (2) The enlarged spleen occupied the whole upper abdomen and contained numerous small cysts in one patient. The patient was initially diagnosed as having a pancreatic tumor because of the location, but color Doppler sonography clearly demonstrated two vessels (artery and vein) running parallel from the center of the mass. This characteristic vascular structure led to the determination that the mass was the markedly enlarged spleen. (3) The splenic lesion was isolated in six patients but was associated with mesenteric and pleural lymphangioma in one symptomatic patient. Conclusions: (1) When US shows multiple cysts of different sizes in the spleen, the diagnosis of splenic lymphangioma is not difficult to make with US and CT alone. (2) Color Doppler sonography is a very useful tool to increase diagnostic confidence because it demonstrates the vasculature of the mass. (3) When examining patients with splenic lymphangioma, one should consider the possibility of multiorgan involvement.


Abdominal Imaging | 2000

Gallbladder carcinoma: color Doppler sonography

Tomoya Komatsuda; Hideaki Ishida; K. Konno; Y. Hamashima; H. Naganuma; M. Sato; Sumio Watanabe

This study, based on color Doppler and pulsed Doppler sonographic results of 13 cases with gallbladder carcinoma, eight cases of adenomyomatosis, and eight cases of tumefactive biliary sludge, shows that the presence or absence of blood flow signals helps in the differentiation between gallbladder carcinoma and tumefactive biliary sludge (84.6% sensitivity and 80.0% specificity). However, color Doppler sonography is still not fully capable of distinguishing all gallbladder carcinoma, and a further increase in Doppler sensitivity is mandatory for this purpose. Visualization of high-velocity blood flow within the lesion made gallbladder carcinoma more likely than benign tumor. In contrast, there was no difference in the resistive index between gallbladder carcinoma, adenomyomatosis, and normal subject groups, and the significance of the resistive index is a subject of future study.


Abdominal Imaging | 2000

Chilaiditi syndrome: sonographic findings

M. Sato; Hideaki Ishida; K. Konno; Y. Hamashima; H. Naganuma; Tomoya Komatsuda; J. Ishida; Sumio Watanabe

AbstractBackground and methods: Sonographic (US) findings of Chilaiditi syndrome have been rarely reported in the literature. We reviewed 18 cases of Chilaiditi syndrome to pinpoint its US pattern. Results: (1) US showed gas echoes of different sizes superimposed over the entire liver in two cases and over the right hepatic lobe in six cases, leading to a high suspicion of Chilaiditi syndrome. (2) US showed a small gas echo in the hepatodiaphragmatic space, mimicking pneumoperitoneum in eight cases. In this instance, altering the patients position allowed for confirmation of the lack of a change in the location of the gas echo, unlike cases of pneumoperitoneum. (3) The hepatic surface appeared as a hyperechoic mass in two cases. Conclusion: Knowledge of US patterns of Chilaiditi syndrome helps avoid confusion with pneumoperitoneum or hepatic masses.


Journal of Clinical Ultrasound | 1998

Color Doppler findings in Castleman's disease of the mesentery

K. Konno; Hideaki Ishida; Y. Hamashima; Tomoya Komatsuda; Osamu Masamune

Castlemans disease is a relatively rare lymphoproliferative disease. We report an asymptomatic case of Castlemans disease isolated to the mesentery and detected incidentally by sonography. In this case, color Doppler sonography demonstrated an artery penetrating the masss hilum, suggesting a lymphatic origin of the lesion, as well as fine accessory peripheral arteries, suggesting malignancy. To our knowledge, there has been no previous report of detailed color Doppler findings in Castlemans disease.


Abdominal Imaging | 1999

Assessment of resectability of pancreatic carcinoma by color Doppler sonography

Hideaki Ishida; K. Konno; Y. Hamashima; H. Naganuma; Tomoya Komatsuda; M. Sato; J. Ishida; Osamu Masamune

This study was undertaken to evaluate the role of color Doppler sonography in the preoperative assessment of vascular involvement in patients with pancreatic carcinoma. Twenty-six pancreatic carcinomas were investigated with color Doppler sonography and angiography, and the results of these examinations were compared with those of surgical findings. Color Doppler sonography was more sensitive than angiography in depicting vascular involvement of carcinoma. Thus, it seems rational to perform a preoperative assessment in suspected pancreatic carcinoma patients initially with color Doppler sonography to improve patient management.


Abdominal Imaging | 1998

Intrahepatic venous collaterals

H. Naganuma; Hideaki Ishida; K. Konno; Tomoya Komatsuda; Y. Hamashima; J. Ishida; Osamu Masamune

Abstract.Background: The aim of this study was to reevaluate the causes and sites of intrahepatic venous collaterals and to determine the role of color Doppler sonography in the diagnosis of this relatively rare vascular abnormality. Methods: Real-time color Doppler sonography was used to study 21 patients with intrahepatic venous collaterals. The cause, distribution, and clinical manifestations of collaterals were determined, and Doppler waveforms obtained from the collaterals were also analyzed. Results: First, the causes of intrahepatic venous collaterals were divided roughly into two groups according to the presence or absence of veno-occlusions. The former group included liver tumors (six cases), primary Budd-Chiari syndrome (five cases), and metastatic adrenal tumors invading the inferior vena cava (two cases). The latter group consisted of diaphragmatic hernia (three cases), Osler-Weber-Rendu disease (two cases), and congestive liver (one case). The cause was not determined in two cases. Second, venous collaterals were distributed throughout the entire liver in primary Budd-Chiari syndrome but localized in the other cases. Third, Doppler waveforms of the collaterals were divided into two patterns: flat flow and multiphasic flow. Flat flow pattern was seen in patients with veno-occlusive diseases, and multiphasic flow pattern was seen in patients without veno-occlusive disease. Conclusion: The relationship between intrahepatic venous collaterals and veno-occlusive diseases has been emphasized in the literature, but the results of our series showed that they occurred under a wide variety of conditions, even without veno-occlusive diseases, including diaphragmatic hernia and Osler-Weber-Rendu disease. The analysis of the Doppler waveforms of the collaterals was useful in differentiating those due to veno-occlusive diseases and those not.


Abdominal Imaging | 1998

Lobar atrophy of the liver

Hideaki Ishida; H. Naganuma; K. Konno; Tomoya Komatsuda; Y. Hamashima; T. Ishioka; Takao Hoshino; J. Ishida; Osamu Masamune

Abstract. Lobar atrophy of the liver due to causes other than liver tumor or liver cirrhosis is a relatively rare pathological condition, and there are only a few reports in the literature. We report six such cases and try to evaluate the relationship between lobar atrophy and portal flow disturbance. The patients could be divided into two groups according to the site of the atrophy: those with atrophy of the left lobe (two cases) and those with atrophy of the right lobe (four cases). The two cases with atrophy of the right lobe had hepatholithiasis in the involved segments, but the cause was not determined in the remaining four cases. In all six cases, portal flow disturbance was noted, including invisibility of the portal vein in four cases, narrowing in one case, and portal thrombus in one case. Collateral circulation was not recognized in any of our cases. Of interest is the mode of lobar atrophy. Atrophy of the right lobe was always associated with marked enlargement of the left lobe, but that of the left lobe did not induce an enlargement of the right lobe.


European Radiology | 2000

Congenital absence of the horizontal portion of the left portal vein: ultrasound findings.

M. Sato; Hideaki Ishida; K. Konno; H. Naganuma; Tomoya Komatsuda; Y. Hamashima; Sumio Watanabe

Abstract. Congenital absence of the horizontal portion of the left portal vein is very rare and has been very reported sporadically. We present three such cases referred from other hospitals with a diagnosis of intrahepatic vascular anomaly. Color Doppler ultrasound not only confirmed the diagnosis but also allowed a quantitative measurement of blood flow in these cases. Although it is a very rare condition, knowledge of the ultrasound and color Doppler findings helps in establishing the diagnosis of this congenital anomaly.


Abdominal Imaging | 1999

Gastrointestinal bleeding due to ruptured pseudoaneurysm in patients with pancreatitis.

Hideaki Ishida; K. Konno; Tomoya Komatsuda; M. Sato; H. Naganuma; Y. Hamashima; J. Ishida

We present the medical imaging results and clinical data of four pancreatitis cases with gastrointestinal bleeding due to rupture of a pseudoaneurysm to determine in which situations a rupture should be suspected. Our observations suggest that the possibility of such a rupture must be kept in mind when encountering not only patients with hematemesis or melena associated with acute severe abdominal symptoms but also patients with severe anemia. Color Doppler sonography and computed tomography are very useful as first-line diagnostic tools and should be performed promptly to prevent a delay in patient management.

Collaboration


Dive into the Y. Hamashima's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

J. Ishida

Tokyo Medical University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge