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Magnetic Resonance in Medicine Aug 2015The pseudo-diffusion coefficient D* in intravoxel incoherent motion (IVIM) imaging was found difficult to seize. Flow-compensated diffusion gradients were used to test...
PURPOSE
The pseudo-diffusion coefficient D* in intravoxel incoherent motion (IVIM) imaging was found difficult to seize. Flow-compensated diffusion gradients were used to test the validity of the commonly assumed biexponential limit and to determine not only D*, but also characteristic timescale τ and velocity v of the incoherent motion.
THEORY AND METHODS
Bipolar and flow-compensated diffusion gradients were inserted into a flow-compensated single-shot EPI sequence. Images were obtained from a pipe-shaped flow phantom and from healthy volunteers. To calculate the IVIM signal outside the biexponential limit, a formalism based on normalized phase distributions was developed.
RESULTS
The flow-compensated diffusion gradients caused less signal attenuation than the bipolar ones. A signal dependence on the duration of the flow-compensated gradients was found at low b-values in the volunteer datasets. The characteristic IVIM parameters were estimated to be v = 4.60 ± 0.34 mm/s and τ = 144 ± 10 ms for liver and v = 3.91 ± 0.54 mm/s and τ = 224 ± 47 ms for pancreas.
CONCLUSION
Our results strongly indicate that the biexponential limit does not adequately model the diffusion signal in liver and pancreas. By using both bipolar and flow-compensated diffusion gradients of different duration, the characteristic timescale and velocity of the incoherent motion can be determined.
Topics: Algorithms; Blood Flow Velocity; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Imaging, Three-Dimensional; Liver Circulation; Magnetic Resonance Angiography; Motion; Phantoms, Imaging; Reproducibility of Results; Sensitivity and Specificity
PubMed: 25116325
DOI: 10.1002/mrm.25410 -
Liver Transplantation : Official... Jun 2015Major hepatectomy or small-for-size liver transplantation may result in postoperative liver failure. So far, no treatment is available to improve liver regeneration....
Major hepatectomy or small-for-size liver transplantation may result in postoperative liver failure. So far, no treatment is available to improve liver regeneration. Herein, we studied whether cilostazol, a selective phosphodiesterase III inhibitor, is capable of improving liver regeneration after major hepatectomy. Sprague-Dawley rats (n = 74) were treated with cilostazol (5 mg/kg daily) or a glucose solution and underwent either 70% liver resection or a sham operation. Before and after surgery, hepatic arterial and portal venous blood flow and hepatic microvascular perfusion were analyzed. Liver morphology, function, and regeneration were studied with histology, immunohistochemistry, western blotting, and bile excretion analysis. Cilostazol significantly increased hepatic blood flow and microcirculation before and after hepatectomy in comparison with sham-operated controls. This was associated with an elevation of hepatic vascular endothelial growth factor expression, an increase of hepatocellular proliferation, and an acceleration of liver regeneration. Furthermore, cilostazol protected the tissue of the remnant liver as indicated by an attenuation of hepatocellular disintegration. In conclusion, cilostazol increases hepatic blood perfusion, microcirculation, and liver regeneration after a major hepatectomy. Thus, cilostazol may represent a novel strategy to reduce the rate of liver failure after both extended hepatectomy and small-for-size liver transplantation.
Topics: Animals; Apoptosis; Bile; Cilostazol; Drug Evaluation, Preclinical; Female; Liver; Liver Circulation; Liver Failure; Liver Regeneration; Models, Animal; Phosphodiesterase 3 Inhibitors; Rats, Sprague-Dawley; Tetrazoles; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A
PubMed: 25772848
DOI: 10.1002/lt.24114 -
Kidney International Apr 2010Cirrhosis induces extra-cellular fluid volume expansion, which when the disease is advanced can be severe and poorly responsive to therapy. Prevention and/or effective... (Review)
Review
Cirrhosis induces extra-cellular fluid volume expansion, which when the disease is advanced can be severe and poorly responsive to therapy. Prevention and/or effective therapy for cirrhotic edema requires understanding the stimulus that initiates and maintains sodium retention. Despite much study, this stimulus remains unknown. Work over the last several years has shown that signals originating in the liver can influence a variety of systemic functions, including extra-cellular fluid volume control. We review work on the afferent mechanisms triggering sodium retention in cirrhosis and suggest that the data are most consistent with the existence of a sensor in the hepatic circulation that contributes to normal extra-cellular fluid volume control (that is, a 'volume' sensor) and that in cirrhosis, the sensor is pathologically activated by the hepatic circulatory abnormalities caused by the disease. Detailed analysis of the hepatic circulation in normal conditions and cirrhosis is needed.
Topics: Body Fluids; Fibrosis; Hepatorenal Syndrome; Humans; Hypernatremia; Liver; Liver Circulation; Liver Cirrhosis
PubMed: 20147888
DOI: 10.1038/ki.2010.4 -
Brazilian Journal of Medical and... Dec 2015This study investigated the value of computed tomography (CT) in the diagnosis and treatment of hepatic veno-occlusive disease (HVOD) caused by Sedum aizoon (SA). The...
This study investigated the value of computed tomography (CT) in the diagnosis and treatment of hepatic veno-occlusive disease (HVOD) caused by Sedum aizoon (SA). The clinical manifestations, treatment results, imaging findings, and histological findings of the liver were analyzed in 39 patients with HVOD caused by SA. Hepatomegaly, liver dysfunction, abdominal effusion, and geographic density changes on liver CT scans were found in all 39 patients. The pathological findings of histological liver examination included swelling and point-like necrosis of liver cells, significant expansion and congestion of the sinuses, endothelial swelling, and wall thickening with incomplete lumen occlusion of small liver vessels. CT geographic density changes were confirmed by histological examination of the liver in 18 patients. Sixteen patients with small amounts of ascites that started within 4 weeks of treatment recovered completely or significantly improved after symptomatic and supportive treatment. However, only 43.75% of the patients with larger amounts of ascites improved following symptomatic and supportive treatment. In conclusion, liver CT examination is a valuable, safe, and noninvasive tool for the diagnosis of HVOD caused by SA. In selected cases, liver CT examination may replace liver biopsy and histological analysis.
Topics: Adult; Aged; Ascites; Biopsy; China; Drugs, Chinese Herbal; Female; Hepatic Veno-Occlusive Disease; Humans; Liver Circulation; Male; Middle Aged; Necrosis; Retrospective Studies; Sedum; Tomography, X-Ray Computed
PubMed: 26517336
DOI: 10.1590/1414-431X20154563 -
British Journal of Clinical Pharmacology May 1986
Topics: Half-Life; Hemodynamics; Humans; Kinetics; Liver; Liver Circulation; Verapamil
PubMed: 3718816
DOI: 10.1111/j.1365-2125.1986.tb02846.x -
Anatomical Record (Hoboken, N.J. : 2007) Jun 2008This review briefly summarizes what is known about the dynamic morphology of the hepatic microvascular system that includes all vessels in the liver with a diameter less... (Review)
Review
This review briefly summarizes what is known about the dynamic morphology of the hepatic microvascular system that includes all vessels in the liver with a diameter less than 300 microm and various morphological sites within these vessels that regulate the distribution of blood flow. The latter include the various segments of the afferent portal venules and hepatic arterioles, the sinusoids, and central and hepatic venules. Sinusoids are unique exchange vessels lined by fenestrated endothelial cells which have important endocytotic functions and phagocytic Kupffer cells which are important for host defense. These are encircled by extraluminal stellate cells that are specialized pericytes containing fat droplets that store vitamin A. The principle sites for regulating blood flow are in the sinusoidal network with stellate and endothelial cells playing a major role in regulating the diameters of sinusoids and the distribution of blood flow in individual sinusoids, lobules, or segments of lobules. The sinusoidal endothelial cells are a sensitive and early target for several toxicants. For example, as early as 30 minutes after the administration of acetaminophen, the endothelial cells become swollen and begin to lose the ability to endocytose ligands. Within 2 hr, gaps through the cytoplasm appear formed by the destruction and/or coalescence of fenestrae which permit red blood cells to penetrate into the space of Disse. Subsequently, the sinusoid may collapse or disintegrate reducing blood flow.
Topics: Acetaminophen; Animals; Corrosion Casting; Endothelial Cells; Humans; Kupffer Cells; Liver; Liver Circulation; Microcirculation; Microscopy, Electron; Models, Anatomic; Models, Cardiovascular
PubMed: 18484612
DOI: 10.1002/ar.20663 -
Minerva Anestesiologica May 2011Severe hyperammonemia (hyperNH3) in neonatal cardiac failure after cardiac surgery is rare. We report a case of a 2470-g female infant born at the week 37 of gestation... (Review)
Review
Severe hyperammonemia (hyperNH3) in neonatal cardiac failure after cardiac surgery is rare. We report a case of a 2470-g female infant born at the week 37 of gestation with complex congenital heart disease (truncus arteriosus type III, interrupted aortic arch and tricuspid valve insufficiency) and hemodynamically non-significant intrahepatic arterio-venous malformation. She developed hyperNH3 (highest NH3 blood level: 467 µmol/L) without severe liver failure (INR of 1.9). The origin of the hyperNH3 was multifactorial including limited capacity of liver detoxification function due to congenital porto-caval shunt, liver ischemia, excessive protein intake and increased protein catabolic rate. HyperNH3 treatment partially succeeded in decreasing ammonia level and included discontinuation of protein intake, administration of phenylacetate and sodium benzoate. This case highlights the fact that NH3 detoxification by the liver has limitations for a neonate with multifactorial causes that decrease liver perfusion.
Topics: Arteriovenous Malformations; Cardiac Surgical Procedures; Fatal Outcome; Female; Heart Failure; Humans; Hyperammonemia; Infant, Newborn; Liver; Liver Circulation; Liver Failure; Liver Function Tests; Postoperative Complications; Tricuspid Valve Insufficiency; Truncus Arteriosus, Persistent
PubMed: 21540812
DOI: No ID Found -
Gut Aug 1998Massive liver necrosis, characteristic of acute liver failure, may affect hepatosplanchnic haemodynamics, and contribute to the alterations in renal haemodynamics and...
BACKGROUND
Massive liver necrosis, characteristic of acute liver failure, may affect hepatosplanchnic haemodynamics, and contribute to the alterations in renal haemodynamics and function.
AIMS
To investigate the relation between hepatosplanchnic haemodynamics, including portal systemic shunting, and renal blood flow and function in rats with acute liver failure.
METHODS
Liver failure was induced in male Wistar rats by intraperitoneal injection of 1.1 g/kg of D(+)-galactosamine hydrochloride. The parameters assessed included; systemic, hepatosplanchnic, and renal blood flow (57Co microsphere method); portal-systemic shunting and intrarenal shunting (consecutive intrasplenic, intraportal, or renal arterial injections of 99mTc methylene diphosphonate and 99mTc albumin microspheres); arterial blood pressure and portal pressure; renal function; and liver function (liver function tests and 14C aminopyrine breath test).
RESULTS
Progressive liver dysfunction was accompanied by the development of a hyperdynamic circulation, a highly significant decrease in renal blood flow and function, and an increase in intrarenal shunting 36, 42, and 48 hours after administration of D-galactosamine. The alterations in renal blood flow and function were accompanied by significant increases in portal pressure, portal venous inflow, and intrahepatic portal systemic shunting in galactosamine treated rats compared with controls. There was a significant correlation between changes in renal blood flow and changes in portal pressure, intrahepatic portal systemic shunting, and deterioration in liver function (r = 0.8, p < 0.0001).
CONCLUSIONS
The results of this study suggest that both increased intrahepatic portal systemic shunting and hepatocyte impairment may contribute to alterations in renal haemodynamics and function.
Topics: Animals; Blood Pressure; Hemodynamics; Hepatic Artery; Liver Circulation; Liver Failure, Acute; Male; Rats; Rats, Wistar; Renal Circulation; Splanchnic Circulation
PubMed: 10189857
DOI: 10.1136/gut.43.2.272 -
Scientific Reports Mar 2021The objective of this study was to compare three different heat transfer models for radiofrequency ablation of in vivo liver tissue using a cooled electrode and three...
The objective of this study was to compare three different heat transfer models for radiofrequency ablation of in vivo liver tissue using a cooled electrode and three different voltage levels. The comparison was between the simplest but less realistic Pennes' equation and two porous media-based models, i.e. the Local Thermal Non-Equilibrium (LTNE) equations and Local Thermal Equilibrium (LTE) equation, both modified to take into account two-phase water vaporization (tissue and blood). Different blood volume fractions in liver were considered and the blood velocity was modeled to simulate a vascular network. Governing equations with the appropriate boundary conditions were solved with Comsol Multiphysics finite-element code. The results in terms of coagulation transverse diameters and temperature distributions at the end of the application showed significant differences, especially between Pennes and the modified LTNE and LTE models. The new modified porous media-based models covered the ranges found in the few in vivo experimental studies in the literature and they were closer to the published results with similar in vivo protocol. The outcomes highlight the importance of considering the three models in the future in order to improve thermal ablation protocols and devices and adapt the model to different organs and patient profiles.
Topics: Blood Coagulation; Blood Flow Velocity; Computer Simulation; Hot Temperature; Humans; Liver; Liver Circulation; Liver Neoplasms; Models, Biological; Porosity; Radiofrequency Ablation; Treatment Outcome
PubMed: 33674658
DOI: 10.1038/s41598-021-84546-6 -
Acta Obstetricia Et Gynecologica... 2009OBJECTIVE. Fetal liver blood supply is an important determinant of fetal growth and adaptation. Most fetal liver blood supply is from the umbilical vein, but the portal...
OBJECTIVE. Fetal liver blood supply is an important determinant of fetal growth and adaptation. Most fetal liver blood supply is from the umbilical vein, but the portal vein contributes 14-20% and studies of low-risk pregnancies suggest the splanchnic arteries are also involved in the homeostasis of fetal liver perfusion. Here we determine the circulatory pattern of the fetal liver in intrauterine growth restriction (IUGR). DESIGN. Cross-sectional study. POPULATION. Thirty-one IUGR fetuses (estimated fetal weight <5th centile). METHODS. Pulsatility index (PI) measurements of the umbilical, middle cerebral, splenic, hepatic, and superior mesenteric arteries were compared with a reference population and related to umbilical venous flow, umbilico-caval pressure gradient (assessed by ductus venosus peak velocity) and venous distribution within the liver (assessed by flow velocity in the left portal vein). RESULTS. Thirteen of 31 IUGR fetuses had umbilical artery PI > 97.5 centile and 13 showed a middle cerebral artery brain-sparing pattern (PI Z-score < - 2). In IUGR, umbilical venous flow was lower and less umbilical blood was distributed to the right liver lobe, while the umbilico-caval pressure gradient was kept normal. The hepatic and splenic arteries, but not the superior mesenteric artery, had low PI compared with the reference population. CONCLUSIONS. IUGR fetuses with increased or normal umbilical artery PI maintained venous perfusion pressure to the liver while distributing less umbilical blood to the right liver lobe. They showed regional splanchnic arterial redistribution with low splenic and hepatic artery PI, implying increased portal venous flow and direct arterial contribution to hepatic perfusion, respectively.
Topics: Adolescent; Adult; Cross-Sectional Studies; Female; Fetal Growth Retardation; Humans; Infant, Newborn; Liver; Liver Circulation; Male; Pregnancy; Pregnancy Trimester, Second; Pulsatilla; Regional Blood Flow; Splanchnic Circulation; Umbilical Arteries; Young Adult
PubMed: 19707895
DOI: 10.1080/00016340903214924