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Douglas B Evans - One of the best experts on this subject based on the ideXlab platform.
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survival following pancreaticoduodenectomy with resection of the superior mesenteric portal vein confluence for adenocarcinoma of the pancreatic head
British Journal of Surgery, 1998Co-Authors: Steven D Leach, Chusilp Charnsangavej, Karen R Cleary, Claudia J Fenoglio, Jeffrey E Lee, Andrew M Lowy, Peter W T Pisters, Douglas B EvansAbstract:Background The survival of patients who underwent pancreaticoduodenectomy with or without en bloc resection of the superior mesenteric–portal vein (SMPV) confluence for adenocarcinoma of the pancreatic head was compared. Methods To be considered for surgery, patients were required to fulfil the following computed tomography criteria for resectability: (1) absence of extrapancreatic disease, (2) no evidence of tumour extension to the superior mesenteric artery (SMA) or coeliac axis, and (3) a patent SMPV confluence. Tumour adherence to the superior mesenteric vein (SMV) or SMPV confluence was assessed at operation and en bloc venous resection was performed when necessary to achieve complete tumour extirpation. Results Seventy-five consecutive patients underwent pancreaticoduodenectomy, 44 without venous resection and 31 with en bloc resection of the SMPV confluence. There were no perioperative deaths in either group; late (more than 6 months) occlusion of the reconstructed SMPV confluence contributed to the death of two patients. Median survival in the 31 patients who required venous resection at the time of pancreaticoduodenectomy was 22 months, and that for the 44 control patients was 20 months (P = 0·25). Conclusion Patients with adenocarcinoma of the pancreatic head who require venous resection during pancreaticoduodenectomy for isolated tumour extension to the SMV or SMPV confluence (in the absence of tumour extension to the SMA or coeliac axis) have a duration of survival no different from that of patients who undergo standard pancreaticoduodenectomy. These data suggest that venous involvement is a function of tumour location rather than an indicator of aggressive tumour biology. © 1998 British Journal of Surgery Society Ltd
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rationale for en bloc vein resection in the treatment of pancreatic adenocarcinoma adherent to the superior mesenteric portal vein confluence
Annals of Surgery, 1996Co-Authors: George M Fuhrman, Steven D Leach, Charles A Staley, James C Cusack, Chusilp Charnsangavej, Karen R Cleary, Adel K Elnaggar, Claudia J Fenoglio, Jeffrey E Lee, Douglas B EvansAbstract:OBJECTIVE: Tumor invasion of the superior mesenteric-portal vein (SMPV) confluence is often considered a contraindication to pancreaticoduodenectomy for patients with malignant tumors of the pancreas or periampullary region. The authors sought to determine whether pancreaticoduodenectomy with en bloc resection of the SMPV confluence could be safely performed and whether tumors involving the SMPV confluence were associated with pathologic parameters suggesting poor prognosis. SUMMARY BACKGROUND DATA: Several centers have reported high rates of retroperitoneal margin positivity after pancreaticoduodenectomy for tumors of the pancreatic head and periampullary region. Positive-margin or incomplete resection is associated with early tumor recurrence and no survival benefit compared with palliative therapy. Tumor adherence to the lateral of posterior wall of the SMPV confluence often represents the only barrier to complete tumor resection at the time of pancreaticoduodenectomy. METHODS: Data on all patients undergoing pancreaticoduodenectomy for adenocarcinoma of the pancreas or periampullary region over a 3.5-year period were entered prospectively in a pancreatic tumor database. To be considered for surgery, patients were required to fulfill the following computed tomography criteria for resectability: 1) the absence of extrapancreatic disease, 2) no tumor encasement of the superior mesenteric artery or celiac axis, and 3) a patent SMPV confluence. Tumor adherence to the superior mesenteric vein or SMPV confluence was assessed intraoperatively, and en bloc venous resection was performed when necessary to achieve complete tumor extirpation. Data on operative characteristics, morbidity, mortality, tumor size, nodal metastases, margin positivity, perineural invasion, and tumor DNA content were compared for patients who did and did not receive venous resection. RESULTS: Fifty-nine patients underwent pancreaticoduodenectomy, 36 without venous resection and 23 with en bloc resection of the SMPV confluence. No differences in median hospital stay, morbidity, mortality, tumor size, margin positivity, nodal positivity, or tumor DNA content were observed between groups. CONCLUSIONS: When necessary, segmental resection of the SMPV confluence may be performed safely during pancreaticoduodenectomy for periampullary malignant tumors. Tumors invading the SMPV confluence are not associated with histologic parameters suggesting a poor prognosis. Our data suggest that venous involvement is a function of tumor location rather than an indicator of aggressive tumor biology.
Tiago Marcos Alves - One of the best experts on this subject based on the ideXlab platform.
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effect of channel tributaries on the evolution of submarine channel confluences espirito santo basin se brazil
Geological Society of America Bulletin, 2020Co-Authors: Tiago Marcos Alves, Jose Antonio Constantine, Davide Gamboa, Shiguo WuAbstract:Confluences are geomorphologic features fed by distinct channel tributaries that record the contribution of multiple sediment sources. They are key features of both fluvial and submarine channels in geomorphologic and sedimentologic terms. Here, we use high-quality three-dimensional seismic data from SE Brazil to document the response of a submarine channel confluence to turbidity currents originating from a tributary. The studied channel system consists of a west tributary, an east tributary, and a postconfluence channel, with the last two comprising the main channel at present. Downstream from the confluence, changes in planform morphology and architecture were found due to the effect of turbidity currents sourced from the west tributary channel. A channel bend in the main channel curved toward the west when it was first formed but later curved toward the east, and so remains until the present day. This process led to the migration of the confluence point ∼500 m to the east, and changed the bed morphology from discordant (where the beds of tributaries and main channels meet at an unequal depth) to concordant (where the beds of tributaries and main channels meet at approximately the same depth). In addition to the channel bend near the confluence, two other bends further downstream recorded significant changes with time, increasing channel sinuosity from 1.11 to 1.72. These three channel bends near the confluence accumulated a large volume of sediment at their inner banks, generating depositional bars. Multiple channel forms within the depositional bars indicate the occurrence of large-scale lateral migration near the confluence. Hence, turbidity currents from the west tributary are shown to influence the submarine channel by promoting lateral channel migration, confluence migration, increases in channel sinuosity, and the formation of large depositional bars. These variations near the confluence reveal a change in tributary activity and a shift in sediment sources from east to west on the continental shelf. Such a shift suggests variations in sedimentary processes on the continental shelf probably due to avulsions on Doce River Delta.
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a submarine channel confluence classification for topographically confined slopes
Marine and Petroleum Geology, 2012Co-Authors: Davide Gamboa, Tiago Marcos Alves, Joe CartwrightAbstract:High-quality 3D seismic data are used in this paper to: a) investigate the geometry of Miocene–Holocene submarinechannels in confluence regions, and b) to correlate the geometry of channelconfluences with the styles of topographic confinement imposed by salt structures in the Espirito Santo Basin (SE Brazil). A new method is used to analyse geomorphic parameters of three channel intervals (Units 1–3) and a modern channel. 5348 Channel Points (CP) are recorded on a sinusoidal slope interrupted by salt structures. In the upper-slope region, diapir confinement directly controls the location of channelconfluences. These are characterised by a sharp increase in channel width and height at their junctions. Scale relationships show an increase in channel width of the order of 1.19 < W < 1.22 in confluence regions. Ratios of channel height between confluence and pre-confluence regions are 1.09 < H < 1.40, with ratios of <1 observed in post-confluence regions. This work proves the existence of a direct relationship between topographic confinement, confluence location and relative channel distribution. The studied submarineconfluences are located in regions with high confinement created by salt diapirs. The results of this work are significant, as they show clustered distribution patterns in channels, with higher channel densities being observed in pre-confluence regions. Thus, we propose a new classification for submarineconfluences based on a combined analysis of channel geometry and seismic attribute data. Confluences may be symmetric or asymmetric based on the equality of the angles the tributaries bear to the post-confluencechannel. Symmetric confluences can be left or right symmetric, based on whether the dominant flow path is in the left- or right-hand tributary. Asymmetric confluences are pure asymmetric or secondary asymmetric depending on whether the dominant flow takes place along the main tributary and the post-confluencechannel alignement, or along the secondary tributary which is at an angle with the main alignement.
Davide Gamboa - One of the best experts on this subject based on the ideXlab platform.
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effect of channel tributaries on the evolution of submarine channel confluences espirito santo basin se brazil
Geological Society of America Bulletin, 2020Co-Authors: Tiago Marcos Alves, Jose Antonio Constantine, Davide Gamboa, Shiguo WuAbstract:Confluences are geomorphologic features fed by distinct channel tributaries that record the contribution of multiple sediment sources. They are key features of both fluvial and submarine channels in geomorphologic and sedimentologic terms. Here, we use high-quality three-dimensional seismic data from SE Brazil to document the response of a submarine channel confluence to turbidity currents originating from a tributary. The studied channel system consists of a west tributary, an east tributary, and a postconfluence channel, with the last two comprising the main channel at present. Downstream from the confluence, changes in planform morphology and architecture were found due to the effect of turbidity currents sourced from the west tributary channel. A channel bend in the main channel curved toward the west when it was first formed but later curved toward the east, and so remains until the present day. This process led to the migration of the confluence point ∼500 m to the east, and changed the bed morphology from discordant (where the beds of tributaries and main channels meet at an unequal depth) to concordant (where the beds of tributaries and main channels meet at approximately the same depth). In addition to the channel bend near the confluence, two other bends further downstream recorded significant changes with time, increasing channel sinuosity from 1.11 to 1.72. These three channel bends near the confluence accumulated a large volume of sediment at their inner banks, generating depositional bars. Multiple channel forms within the depositional bars indicate the occurrence of large-scale lateral migration near the confluence. Hence, turbidity currents from the west tributary are shown to influence the submarine channel by promoting lateral channel migration, confluence migration, increases in channel sinuosity, and the formation of large depositional bars. These variations near the confluence reveal a change in tributary activity and a shift in sediment sources from east to west on the continental shelf. Such a shift suggests variations in sedimentary processes on the continental shelf probably due to avulsions on Doce River Delta.
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a submarine channel confluence classification for topographically confined slopes
Marine and Petroleum Geology, 2012Co-Authors: Davide Gamboa, Tiago Marcos Alves, Joe CartwrightAbstract:High-quality 3D seismic data are used in this paper to: a) investigate the geometry of Miocene–Holocene submarinechannels in confluence regions, and b) to correlate the geometry of channelconfluences with the styles of topographic confinement imposed by salt structures in the Espirito Santo Basin (SE Brazil). A new method is used to analyse geomorphic parameters of three channel intervals (Units 1–3) and a modern channel. 5348 Channel Points (CP) are recorded on a sinusoidal slope interrupted by salt structures. In the upper-slope region, diapir confinement directly controls the location of channelconfluences. These are characterised by a sharp increase in channel width and height at their junctions. Scale relationships show an increase in channel width of the order of 1.19 < W < 1.22 in confluence regions. Ratios of channel height between confluence and pre-confluence regions are 1.09 < H < 1.40, with ratios of <1 observed in post-confluence regions. This work proves the existence of a direct relationship between topographic confinement, confluence location and relative channel distribution. The studied submarineconfluences are located in regions with high confinement created by salt diapirs. The results of this work are significant, as they show clustered distribution patterns in channels, with higher channel densities being observed in pre-confluence regions. Thus, we propose a new classification for submarineconfluences based on a combined analysis of channel geometry and seismic attribute data. Confluences may be symmetric or asymmetric based on the equality of the angles the tributaries bear to the post-confluencechannel. Symmetric confluences can be left or right symmetric, based on whether the dominant flow path is in the left- or right-hand tributary. Asymmetric confluences are pure asymmetric or secondary asymmetric depending on whether the dominant flow takes place along the main tributary and the post-confluencechannel alignement, or along the secondary tributary which is at an angle with the main alignement.
Wu Shiguo - One of the best experts on this subject based on the ideXlab platform.
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The effect of channel tributaries on the evolution of submarine channel confluences (Espírito Santo Basin, SE Brazil)
'Geological Society of America', 2020Co-Authors: Qin Yongpeng, Alves, Tiago M., Constantine, Jose Antonio, Gamboa Davide, Wu ShiguoAbstract:Confluences are geomorphologic features fed by distinct channel tributaries that record the contribution of multiple sediment sources. They are key features of both fluvial and submarine channels in geomorphologic and sedimentologic terms. Here, we use high-quality three-dimensional seismic data from SE Brazil to document the response of a submarine channel confluence to turbidity currents originating from a tributary. The studied channel system consists of a west tributary, an east tributary, and a postconfluence channel, with the last two comprising the main channel at present. Downstream from the confluence, changes in planform morphology and architecture were found due to the effect of turbidity currents sourced from the west tributary channel. A channel bend in the main channel curved toward the west when it was first formed but later curved toward the east, and so remains until the present day. This process led to the migration of the confluence point ∼500 m to the east, and changed the bed morphology from discordant (where the beds of tributaries and main channels meet at an unequal depth) to concordant (where the beds of tributaries and main channels meet at approximately the same depth). In addition to the channel bend near the confluence, two other bends further downstream recorded significant changes with time, increasing channel sinuosity from 1.11 to 1.72. These three channel bends near the confluence accumulated a large volume of sediment at their inner banks, generating depositional bars. Multiple channel forms within the depositional bars indicate the occurrence of large-scale lateral migration near the confluence. Hence, turbidity currents from the west tributary are shown to influence the submarine channel by promoting lateral channel migration, confluence migration, increases in channel sinuosity, and the formation of large depositional bars. These variations near the confluence reveal a change in tributary activity and a shift in sediment sources from east to west on the continental shelf. Such a shift suggests variations in sedimentary processes on the continental shelf probably due to avulsions on Doce River Delta
Shiguo Wu - One of the best experts on this subject based on the ideXlab platform.
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effect of channel tributaries on the evolution of submarine channel confluences espirito santo basin se brazil
Geological Society of America Bulletin, 2020Co-Authors: Tiago Marcos Alves, Jose Antonio Constantine, Davide Gamboa, Shiguo WuAbstract:Confluences are geomorphologic features fed by distinct channel tributaries that record the contribution of multiple sediment sources. They are key features of both fluvial and submarine channels in geomorphologic and sedimentologic terms. Here, we use high-quality three-dimensional seismic data from SE Brazil to document the response of a submarine channel confluence to turbidity currents originating from a tributary. The studied channel system consists of a west tributary, an east tributary, and a postconfluence channel, with the last two comprising the main channel at present. Downstream from the confluence, changes in planform morphology and architecture were found due to the effect of turbidity currents sourced from the west tributary channel. A channel bend in the main channel curved toward the west when it was first formed but later curved toward the east, and so remains until the present day. This process led to the migration of the confluence point ∼500 m to the east, and changed the bed morphology from discordant (where the beds of tributaries and main channels meet at an unequal depth) to concordant (where the beds of tributaries and main channels meet at approximately the same depth). In addition to the channel bend near the confluence, two other bends further downstream recorded significant changes with time, increasing channel sinuosity from 1.11 to 1.72. These three channel bends near the confluence accumulated a large volume of sediment at their inner banks, generating depositional bars. Multiple channel forms within the depositional bars indicate the occurrence of large-scale lateral migration near the confluence. Hence, turbidity currents from the west tributary are shown to influence the submarine channel by promoting lateral channel migration, confluence migration, increases in channel sinuosity, and the formation of large depositional bars. These variations near the confluence reveal a change in tributary activity and a shift in sediment sources from east to west on the continental shelf. Such a shift suggests variations in sedimentary processes on the continental shelf probably due to avulsions on Doce River Delta.