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Hepatic Vasculature (hepatic + vasculature)
Selected AbstractsMolecular characterization of the vascular features of focal nodular hyperplasia and hepatocellular adenoma: A role for angiopoietin-1,HEPATOLOGY, Issue 2 2010Annette S. H. Gouw Focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) are two hepatic nodular lesions of different etiologies. FNH, a polyclonal lesion, is assumed to be a regenerative reaction following a vascular injury, whereas HCA is a monoclonal, benign neoplastic lesion. In addition to features that are predominantly found in either FNH or HCA (e.g., dystrophic vessels in FNH and single arteries in HCA), FNH and HCA share morphological vascular abnormalities such as dilated sinusoids. We hypothesized that these anomalous vascular features are associated with altered expression of growth factors involved in vascular remodeling. This was based on reports of morphologically abnormal hepatic vasculature and nodular lesions in transgenic models of hepatocytic overexpression of angiopoietin-1 (Ang-1), a member of the angiopoietin family, which is crucially involved in vascular morphogenesis and homeostasis. We investigated gene and protein expression of members of the angiopoietin system and vascular endothelial growth factor A (VEGF-A) and its receptors in 9 FNH samples, 13 HCA samples, and 9 histologically normal livers. In comparison with normal samples, a significant increase in Ang-1 was found in FNH (P < 0.01) and HCA (P < 0.05), whereas no significant changes in Ang-2, receptor tyrosine kinase with immunoglobulin-like and EGF-like domains 2, VEGF-A, or vascular endothelial growth factor receptor 2 (VEGFR-2) were observed. Conclusion: Because of the different etiological contexts of a preceding vascular injury in FNH and a neoplastic growth in HCA, Ang-1 might exert different effects on the vasculature in these lesions. In FNH, it could predominantly stimulate recruitment of myofibroblasts and result in dystrophic vessels, whereas in HCA, it may drive vascular remodeling that produces enlarged vessels and arterial sprouting that generates single arteries. Hepatology 2010 [source] Regulatory processes interacting to maintain hepatic blood flow constancy: Vascular compliance, hepatic arterial buffer response, hepatorenal reflex, liver regeneration, escape from vasoconstrictionHEPATOLOGY RESEARCH, Issue 11 2007W. Wayne Lautt Constancy of hepatic blood flow (HBF) is crucial for several homeostatic roles. The present conceptual review focuses on interrelated mechanisms that act to maintain a constant HBF per liver mass. The liver cannot directly control portal blood flow (PF); therefore, these mechanisms largely operate to compensate for PF changes. A reduction in PF leads to reduced intrahepatic distending pressure, resulting in the highly compliant hepatic vasculature passively expelling up to 50% of its blood volume, thus adding to venous return, cardiac output and HBF. Also activated immediately upon reduction of PF are the hepatic arterial buffer response and an HBF-dependent hepatorenal reflex. Adenosine is secreted at a constant rate into the small fluid space of Mall which surrounds the terminal branches of the hepatic arterioles, portal venules and sensory nerves. The concentration of adenosine is regulated by washout into the portal venules. Reduced PFreduces the washout and the accumulated adenosine causes dilation of the hepatic artery, thus buffering the PF change. Adenosine also activates hepatic sensory nerves to cause reflex renal fluid retention, thus increasing circulating blood volume and maintaining cardiac output and PF. If these mechanisms are not able to maintain total HBF, the hemodynamic imbalance results in hepatocyte proliferation, or apoptosis, by a shear stress/nitric oxide-dependent mechanism, to adjust total liver mass to match the blood supply. These mechanisms are specific to this unique vascular bed and provide an excellent example of multiple integrative regulation of a major homeostatic organ. [source] The histological features of microwave coagulation therapy: an assessment of a new applicator designINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 1 2003Benjamin Swift Abstract. Microwave ablation of tumours within the liver may become an adjunct or alternative to resection in patients with primary or secondary cancers. This technique combines the benefits of a large, localized coagulative effect with a single insertion of the applicator, in a significantly shorter time than comparable treatments. A new range of microwave applicators were developed and tested in animal models and both ex-vivo and in-vivo specimens of human liver at resection. At laparotomy, the applicator tip was inserted into normal liver parenchyma and tumours, with each specimen subjected to irradiation for 180 s or more and at varying power outputs. On sectioning an area of spherical blanching was observed around the applicator cavity. Microscopically a zone of coagulative necrosis was seen adjacent to the site of probe insertion. Damage to blood vessels and bile ducts occurred distal to the probe cavity suggesting the passage of heated fluid, a finding that was diminished by temporary occlusion of the hepatic vasculature (a Pringle manoeuvre). Ultra-structural damage was confirmed within the burn zone and selected liver enzymes were shown to be functioning beyond this region. We suggest this indicates the surrounding liver parenchyma is functioning normally and therefore the volume of microwave-induced damage is controllable. We are confident that the new applicator design will allow the effective treatment of larger tumours in a safe and controlled manner with a single application of energy. [source] Unusual hepatic-portal-systemic shunting demonstrated by Doppler sonography in children with congenital hepatic vein ostial occlusionJOURNAL OF CLINICAL ULTRASOUND, Issue 4 2004Maha Barakat MD Abstract Purpose This report describes unusual changes in the hepatic vasculature in 3 children presenting with upper gastrointestinal hemorrhage. Methods The study included 3 children (ages 5,8 years) who presented with hematemesis. All had mild hepatosplenomegaly and normal liver function. Esophageal varices were demonstrated in all on upper endoscopy. Color and spectral Doppler sonography was performed to assess the hepatic vasculature, including the hepatic veins (HVs), portal vein (PV), hepatic artery (HA), and inferior vena cava (IVC). Results The HVs were all patent but with ostial occlusion at the point of their communication with the IVC. Complete flow reversal was shown inside the HVs, with blood draining into collateral vessels at the liver surface and paraumbilical vein. In one patient, the paraumbilical vein could be traced to its communication with the right external iliac vein. In all children, the direction of flow in the PV, HA, and IVC was normal. After endoscopic sclerotherapy, all children were shown to be in good general condition and to have normal liver function for a follow-up period of 15,36 months. Conclusions Ostial occlusion of the HV is a rare cause of hepatic outflow obstruction in children. Doppler sonography is a valuable, noninvasive imaging technique for evaluation of the hepatic vasculature and the accompaning shunting pathways in such cases. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:172,178, 2004; Published online in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/jcu.20019 [source] Negative impact of systemic catecholamine administration on hepatic blood perfusion after porcine liver transplantationLIVER TRANSPLANTATION, Issue 2 2005Arianeb Mehrabi Catecholamines are often administered during and after liver transplantation (LTx) to support systemic perfusion and to increase organ oxygen supply. Some vasoactive agents can compromise visceral organ perfusion. We followed the hypothesis that the vasculature of transplanted livers presents with a higher sensitivity, which leads to an increased vulnerability for flow derangement after application of epinephrine (Epi) or norepinephrine (NorEpi). Hepatic macroperfusion and microperfusion during systemic Epi or NorEpi infusion were measured by Doppler flow and thermodiffusion probes in porcine native, denervated, and transplanted livers (n = 16 in each group). Epi or NorEpi were infused (n = 8 in each subgroup) in predefined dosages (low dose = 5 ,g/kg/minute and high dose = 10 ,g/kg/minute) over 240 minutes. Systemic cardiocirculatory parameters were monitored continuously. Hepatic perfusion data were compared between all groups at comparable time points and dosages. In all native, denervated, and transplanted liver groups, Epi and NorEpi induced an inconsistent rise of mean arterial pressure and heart rate shortly after onset of infusion in both dosages compared with baseline. No significant differences of cardiovascular parameters at comparable time points were observed. In native livers, Epi and NorEpi induced only temporary alterations of hepatic macrocirculation and microcirculation, which returned to baseline 2 hours after onset of infusion. No significant alterations of hepatic blood flow were detected after isolated surgical denervation of the liver. By contrast, transplanted livers showed a progressive decline of hepatic macrocirculation (33,75% reduction) and microcirculation (39,58% reduction) during catecholamine infusions in a dose-dependent fashion. Characteristics of liver blood flow impairment were comparable for both vasoactive agents. In conclusion, pronounced disturbances of hepatic macrocirculation and microcirculation were observed during systemic Epi and NorEpi infusion after LTx compared with native and denervated livers. Microcirculation disturbances after LTx might be explained by impairment of hepatic blood flow regulation caused by an increased sensitivity of hepatic vasculature after ischemia-reperfusion and by lengthening of vasopressor effects caused by reduced hepatocyte metabolism. Clinicians should be aware of this potentially hazardous effect. Therefore, application of catecholamines after clinical LTx should be indicated carefully. (Liver Transpl 2005;11:174,187.) [source] The safety and efficacy of ablative techniques adjacent to the hepatic vasculature and biliary systemANZ JOURNAL OF SURGERY, Issue 1-2 2010Christopher D. Mann Abstract Ablative techniques may provide an alternative to resection in treating awkwardly placed hepatic malignancy adjacent to major vascular and biliary structures. The heat-sink effect may reduce efficacy adjacent to major vascular structures. Vascular occlusion improves efficacy but is associated with increased vascular and biliary complications. The safety and efficacy of ablation in these situations remain to be defined. Further studies comparing both safety and efficacy are needed. [source] | ||||||||||