A novel imaging tool for hepatic portal system using phase contrast technique with hydrogen peroxide-generated O2 gas.

The objective of this study was to investigate the potential of hydrogen peroxide-generated oxygen gas-based phase contrast imaging (PCI) for visualizing mouse hepatic portal veins. The O2 gas was made from the reaction between H2O2 and catalase. The gas production was imaged by PCI in real time. The H2O2 was injected into the enteric cavity of the lower sigmoid colon to produce O2 in the submucosal venous plexus. The generated O2 gas could be finally drained into hepatic portal veins. Absorption contrast imaging (ACI) and PCI of O2-filled portal veins were performed and compared. PCI offers high resolution and real-time visualization of the O2 gas production. Compared with O2-based ACI, O2-based PCI significantly enhanced the revealing of the portal vein in vivo. It is concluded that O2-based PCI is a novel and promising imaging modality for future studies of portal venous disorders in mice models.

Mitochondrial Ca²âº handling is crucial for generation of rhythmical Ca²âº waves in vascular interstitial cells from rabbit portal vein.

Vasomotion is the rhythmical changes in vascular tone of various blood vessels. It was proposed that in rabbit portal vein (RPV) the spontaneous contractile activity is driven by vascular interstitial cells (VICs), since RPV VICs generate rhythmical changes in intracellular Ca(2+) concentration ([Ca(2+)]i) associated with membrane depolarisation in these cells. In this work, using confocal imaging in Fluo-3 loaded RPV VICs we studied if generation of rhythmical [Ca(2+)]i changes is affected when Ca(2+) handling by mitochondria is compromised. We also visualised mitochondria in VICs using Mito Tracker Green fluorescent dye. Our results showed that freshly dispersed RPV VICs generated rhythmical [Ca(2+)]i oscillations with a frequency of 0.2-0.01 Hz. Imaging of VICs stained with Mito Tracker Green revealed abundant mitochondria in these cells with a higher density of the organelles in sub-plasmalemmar region compared to the central region of the cell. Oligomycin, an ATP synthase inhibitor, did not affect the amplitude and frequency of rhythmical [Ca(2+)]i oscillations. In contrast, two uncoupling agents, carbonylcyanide-3-chlorophenylhydrazone (CCCP) and carbonylcyanide-4-trifluoromethoxyphenylhydrazone (FCCP) effectively abolished rhythmical [Ca(2+)]i changes with simultaneous increase in basal [Ca(2+)]i in RPV VICs. These data suggest that in RPV VICs mitochondrial Ca(2+) handling is important for the generation of rhythmical [Ca(2+)]i changes which underlie the spontaneous rhythmical contractile activity in this vessel.

Positive C4d staining of the portal vein endothelium in the liver of patients with biliary atresia: a role of humoral immunity in ongoing liver fibrosis.

PURPOSE: This study aimed to clarify the role of complement activation in fibrogenesis in BA. METHODS: In total, 27 paraffin-embedded liver biopsy samples were immunohistochemically analyzed using C4d polyclonal antibody, vascular cell adhesion molecule-1 (VCAM-1), and CD45. The liver samples were obtained from 25 patients during Kasai operation, and two additional specimens were obtained from 2 patients by needle biopsy later at the time of liver function deterioration. The degree of liver fibrosis was histologically graded 1-3. RESULTS: Among the 25 samples, 9 showed C4d-positive immunostaining localized on the endothelia of a few portal veins in the portal tract. The degree of fibrosis was correlated with C4d staining (p = 0.025). The age at Kasai operation correlated with the degree of fibrosis and the C4d positivity. Two needle biopsy samples were positive for C4d. Among 13 samples submitted for VCAM-1 staining, 2 negative samples were C4d negative and all positive C4d samples were VCAM-1 positive with CD45 mononuclear cell infiltration. CONCLUSION: These findings suggest that ongoing cirrhosis could be a result of progressive "vasculopathy" of the portal vein caused by humoral and cell-mediated immune interaction.

Treatment and education reduce the severity of schistosomiasis periportal fibrosis.

INTRODUCTION: This study evaluates the factors associated with the development of severe periportal fibrosis in patients with Schistosoma mansoni. METHODS: A cross-sectional study was conducted from April to December 2012 involving 178 patients infected with S. mansoni who were treated in the Hospital das Clínicas of Pernambuco, Brazil. Information regarding risk factors was obtained using a questionnaire. Based on the patients' epidemiological history, clinical examination, and upper abdomen ultrasound evaluation, patients were divided into 2 groups: 137 with evidence of severe periportal fibrosis and 41 patients without fibrosis or with mild or moderate periportal fibrosis. Univariate and multivariate analyses were conducted using EpiInfo software version 3.5.5. RESULTS: Illiterate individuals (30.1%) and patients who had more frequent contact with contaminated water in towns in the Zona da Mata of Pernambuco (33.2%) were at greater risk for severe periportal fibrosis. Based on multivariate analysis, it was determined that an education level of up to 11 years of study and specific prior treatment for schistosomiasis were preventive factors for severe periportal fibrosis. CONCLUSIONS: The prevailing sites of the severe forms of periportal fibrosis are still within the Zona da Mata of Pernambuco, although there has been an expansion to urban areas and the state coast. Specific treatment and an increased level of education were identified as protective factors, indicating the need for implementing social, sanitary, and health education interventions aimed at schistosomiasis to combat the risk factors for this major public health problem.

Treatment and education reduce the severity of schistosomiasis periportal fibrosis

Introduction This study evaluates the factors associated with the development of severe periportal fibrosis in patients with Schistosoma mansoni. Methods A cross-sectional study was conducted from April to December 2012 involving 178 patients infected with S. mansoni who were treated in the Hospital das Clínicas of Pernambuco, Brazil. Information regarding risk factors was obtained using a questionnaire. Based on the patients' epidemiological history, clinical examination, and upper abdomen ultrasound evaluation, patients were divided into 2 groups: 137 with evidence of severe periportal fibrosis and 41 patients without fibrosis or with mild or moderate periportal fibrosis. Univariate and multivariate analyses were conducted using EpiInfo software version 3.5.5. Results Illiterate individuals (30.1%) and patients who had more frequent contact with contaminated water in towns in the Zona da Mata of Pernambuco (33.2%) were at greater risk for severe periportal fibrosis. Based on multivariate analysis, it was determined that an education level of up to 11 years of study and specific prior treatment for schistosomiasis were preventive factors for severe periportal fibrosis. Conclusions The prevailing sites of the severe forms of periportal fibrosis are still within the Zona da Mata of Pernambuco, although there has been an expansion to urban areas and the state coast. Specific treatment and an increased level of education were identified as protective factors, indicating the need for implementing social, sanitary, and health education interventions aimed at schistosomiasis to combat the risk factors for this major public health problem. .

Structural organization of hepatic portal vein in rat with special reference to musculature, intimal folds, and endothelial cell alignment.

Structural organization of hepatic portal vein (HPV) was examined in adult rats by means of light and electron microscopy. Three characteristic features were found in the wall structure of rat HPV. (1) Tunica media consisted of two kinds of smooth muscle. The inner circular smooth muscle (CSM) was composed with one or two layer of smooth muscle cells, and was found in the entire length of the HPV and its tributaries. The outer longitudinal smooth muscle (LSM) was limited to a specific region of HPV; in particular it was well-developed at distal half of HPV. CSM counteracts luminal hydrostatic pressure to prevent circumferential hyperextension of venous wall, whereas LSM is likely to counteract a tractive force produced by gravity and movement of small intestine. (2) Intima of HPV showed a unique feature, intimal folds, which protruded into the lumen and were aligned almost circumferentially. Intimal folds were found only at the same region where the LSM was well-developed. Thus, LSM is presumably involved in the formation of intimal folds. (3) The endothelial cells between intimal folds were circumferentially aligned along the folds, although those in the other regions of HPV were arrayed along the longitudinal axis of HPV or the direction of blood flow as reported in other kinds of blood vessel. This finding implied that the circumferential blood flow locally occurs on the surface of intima between the intimal folds.

Scanning electron microscopic study of vascular and biliary casts in chicken and duck liver.

Avian liver is structurally different from that of mammal. There are only a few reports about the ultrastructure of the hepatic vessels and bile duct in birds. Casts of the hepatic vessels and bile ducts in chicken and duck were examined by a scanning electron microscope (SEM) to provide further detail. The sinusoidal vessels formed regular three-dimensional networks but the replicated bile ducts formed irregular ones. There was a dense plexiform network around each tubular cavity in biliary casts. This biliary plexus formed around a small branch of the portal vein. It was the transition between the bile capillaries and ductules. The present study shows that the liver of chicken and duck had the characteristic structure at the peripheral part of biliary system, i.e., biliary plexus.

Avaliação da concordância entre ressonância magnética de ultra-sonografia na classificação de fibrose periportal em esquitossomóticos, segundo a classificação de Niamey / Agreement between magnetic resonance imaging and ultrasonography in the classification of schistosomal periportal fibrosis, according to Niamey's criteria

OBJETIVO: Avaliar a reprodutibilidade da ressonância magnética e a concordância entre a ultra-sonografia e a ressonância magnética na classificação da fibrose periportal em pacientes esquistossomóticos, segundo os critérios qualitativos de Niamey. MATERIAIS E MÉTODOS: Foi realizado estudo prospectivo e duplo-cego, entre fevereiro de 2005 e junho de 2006, em 20 pacientes (10 homens e 10 mulheres, idades entre 24 e 60 anos, média de 42,75 anos) com diagnóstico de esquistossomose mansônica. As imagens de ultra-sonografia e de ressonância magnética foram avaliadas por dois examinadores experientes de forma independente. Foi medida a concordância interobservador para a ressonância magnética e entre a ressonância magnética e a ultra-sonografia. RESULTADOS: A ressonância magnética apresentou resultados concordantes entre os observadores em 14 pacientes (70 por cento). Quando comparamos a ressonância magnética com a ultra-sonografia, obtivemos concordância em apenas seis pacientes pelo observador 1 (30 por cento) e em oito pacientes pelo observador 2 (40 por cento). CONCLUSÃO: A ressonância magnética tem boa reprodutibilidade na avaliação de fibrose periportal em pacientes com esquistossomose avançada, porém sua concordância com a ultra-sonografia é fraca.

OBJECTIVE: To evaluate the reproducibility of magnetic resonance imaging and the agreement between ultrasound and magnetic resonance imaging in the classification of periportal fibrosis in patients with schistosomiasis based on Niamey's qualitative criteria. MATERIALS AND METHODS: A prospective, double-blinded study was conducted between February 2005 and June 2006 with 20 patients (10 men and 10 women, with ages ranging between 24 and 60 years, mean age 42.7 years) diagnosed with schistosomiasis mansoni. Both ultrasound and magnetic resonance images were independently evaluated by two experienced observers. Interobserver agreement was evaluated for findings of periportal fibrosis on magnetic resonance images and in a comparison between magnetic resonance and ultrasound images. RESULTS: The analysis of magnetic resonance images showed total interobserver agreement in 14 patients (70 percent). The comparison between ultrasound and magnetic resonance imaging showed agreement between images in only six cases (30 percent) by observer 1, and in eight cases (40 percent) by observer 2. CONCLUSION: Magnetic resonance imaging presents a good reproducibility in the evaluation of periportal fibrosis in later stages of schistosomiasis, however, the correlation between magnetic resonance imaging and ultrasound is poor.

Three-dimensional organization of the hepatic artery terminal branches: a scanning electron microscopic study of vascular corrosion casts of rat liver.

The hepatic artery plays an important role in the nourishment of liver parenchyma. The arterial distribution generates debate on where the artery terminates in the liver although is accepted that terminal branching of hepatic artery opened into sinusoids and form arterio-portal anastomosis. This implies that sinusoids are fed by both arterial and portal vessels characterized by different pressures. The presence of a double feeding to the sinusoids from the vena porta, at a pressure of 6-7 cm H2O, and from the hepatic artery, at a pressure of 12-25 cm H2O, has generated many studies for the need to explain the prevalence of flow from the vena porta. For this reason, we have studied the terminal hepatic artery branches in the rat by using special microvascular corrosion casting procedure which makes possible to better follow the hepatic artery terminal branches. Twelve young sexually mature male and female Wistar rats were used in this study. More than one hundred vascular corrosion casts of terminal hepatic arterioles were studied by Scanning Electron Microscopy. Histological samples were prepared using standard techniques for light microscopy. The experimental approach allow to easily follow the three-dimensional course of hepatic artery branches which is extremely difficult in standard injections. In all our observations of the rat liver vascular corrosion casts, terminal hepatic artery branches do not end directly in the sinusoidal beds. Terminal hepatic artery branches end into peribiliary plexus, periportal plexus and single capillaries of the portal space. We have not found any arterio-venous shunt nor any arterial vessel flowing into a venous vessel or a sinusoid. This means that only venous blood at a lowered pressure reaches the vena porta branches and the sinusoids.

[Portal reconstruction in hepatectomy with resection of portal vein].

Modern issues of the portal vein resection while hepatectomy conduction are enlighten. The indications for resection of region of the portal vein branches confluence were substantiated, various methods of portoplasty were depicted. New methods of the portal tract passability restoration in discrepancy of diameters of the sutured portal vein portions were proposed. The results of hepatectomy with the portal vein resection were studied up.

Interstitial cells in the vasculature.

Interstitial cells of Cajal are believed to play an important role in gastrointestinal tissues by generating and propagating electrical slow waves to gastrointestinal muscles and/or mediating signals from the enteric nervous system. Recently cells with similar morphological characteristics have been found in the wall of blood vessels such as rabbit portal vein and guinea pig mesenteric artery. These non-contractile cells are characterised by the presence of numerous processes and were easily detected in the wall of the rabbit portal vein by staining with methylene blue or by antibodies to the marker of Interstitial Cells of Cajal c-kit. These vascular cells have been termed "interstitial cells" by analogy with interstitial cells found in the gastrointestinal tract. Freshly dispersed interstitial cells from rabbit portal vein and guinea pig mesenteric artery displayed various Ca2+-release events from endo/sarcoplasmic reticulum including fast localised Ca2+ transients (Ca2+ sparks) and longer and slower Ca2+ events. Single interstitial cells from the rabbit portal vein, which is a spontaneously active vessel, also demonstrated rhythmical Ca2+ oscillations associated with membrane depolarisations, which suggests that in this vessel interstitial cells may act as pacemakers for smooth muscle cells. The function of interstitial cells from the mesenteric arteries is yet unknown. This article reviews some of the recent findings regarding interstitial cells from blood vessels obtained by our laboratory using electron microscopy, immunohistochemistry, tight-seal patch-clamp recording, and fluorescence confocal imaging techniques.

Fine structure of the mouse portal vein in relation to its peristaltic movement.

The hepatic portal vein has been known to make a spontaneous peristaltic movement in some mammals, including the mouse and rat. To investigate the fine structure of the portal vein in relation to its physiological characteristics, we observed the mouse portal vein by using various histological techniques including conventional light microscopy, videomicroscopy, transmission and scanning electron microscopy, and real-time confocal laser scanning microscopy. The mouse hepatic portal vein was provided with a spiral fold which was produced by the inner layer, i.e. the endothelium and smooth muscles of the wall protruding into the lumen. Longitudinal smooth muscle cells spanned the interval of the fold, like a spirally arranged palisade around the vessel wall. The longitudinal muscle fibers ended at the spiral fold, being partly connected with a network of irregularly shaped smooth muscle cells. This network, hitherto unknown, was recognized to be restricted to the fold in distribution and characterized by numerous gap junctions connecting the muscle cells. Real-time confocal laser scanning microscopy using a Ca2+ sensitive fluorescent dye revealed that a transient and periodic increase in Ca2+ concentration occurred in the longitudinal smooth muscle cells and was transmitted spirally from the intestinal to the hepatic side. These findings indicate that, during the peristaltic movement, the contraction of smooth muscle cells is transmitted along the longitudinal smooth muscles of the portal vein wall toward the liver, presumably controlled by the network of the irregularly-shaped smooth muscle cells in the fold of the portal vein. Light microscopic observation in some specimens indicated an occurrence of cardiac muscle cells outside the smooth muscle layer. Restricted to the site of the porta hepatis in distribution, their involvement in the peristaltic contraction of the portal vein seemed unlikely.

Hepatic neovascularization after partial portal vein ligation: novel mechanism of chronic regulation of blood flow.

The present study was undertaken to investigate hepatic microcirculatory response following partial portal vein ligation (PPVL) in rats. Portal pressure was markedly increased 2-6 wk after PPVL, but no significant reduction in sinusoidal perfusion and hepatocellular injury were detected. However, marked neovascularization was observed in PPVL rats using intravital microscopy and scanning electron microscopy (SEM). Extremely high red blood cell velocity (2,000-4,900 microm/s) was seen in these vessels. Injection of fluorescein sodium via the carotid artery revealed that the neovessels originated from the hepatic arterial vasculature. This was further confirmed by clamping the common hepatic artery and phenylephrine injection from the carotid artery. These vessels maintained sufficient flow after massive sinusoidal shutdown elicited by the portal infusion of endothelin receptor B agonist IRL-1620. SEM also showed extensive neovascularization at the hilum. Additionally, clamping the portal vein decreased sinusoidal perfusion only by 9.5% in PPVL, whereas a 71.2% decrease was observed in sham. These results strongly suggest that the liver maintains its microcirculatory flow by vascular remodeling from the hepatic arterial vasculature following PPVL.

Collagen alteration in vascular remodeling by hemodynamic factors.

The collagen alterations in the vascular wall remodeled by hemodynamic change were investigated by electron microscopy and immunohistochemistry. The left anterior descending coronary artery (LAD) without a myocardial bridge (MB) showed both lower matrix metalloproteinase-1 (MMP-1) expression and a smaller extent of spiraled collagen (SC) distribution than the LAD wall with MB, in which the intima was influenced by high shear stress. In the wall of the varicose great saphenous vein (GSV) the expression of MMP-1 was lower, while the expression of prolyl 4-hydroxylase was higher, than in the normal GSV. The extent of SC distribution in the intima and media of the varicose GSV was smaller than that in the normal GSV. An analogous difference in results was demonstrated between the portal vein (PV) of patients with liver cirrhosis and normal PV. However, the levels of expression of MMP-2, MMP-9 and tissue inhibitors of MMP (TIMPs) in these pathologic vessels were not different from those in the corresponding normal vessels. The results indicate that hemodynamic forces such as shear stress and increased intravascular blood pressure contribute to the collagen alterations in the vascular wall, which may lead to vascular wall remodeling.

Endothelin-1-induced vasoconstriction causes a significant increase in portal pressure of rat liver: localized constrictive effect on the distal segment of preterminal portal venules as revealed by light and electron microscopy and serial reconstruction.

Intraportal infusion of endothelin-1 (ET-1), a potent vasoconstrictor, significantly elevates portal venous pressure. To determine the major site of vascular constriction in the intrahepatic porto-sinusoidal system, we performed an in situ perfusion of rat livers with 1 nmol/L ET-1 at a flow rate of 20 mL/min. Portal pressure rose from 22 cm H2O to 54 cm H2O within 25 minutes. Specimens were prepared for light-microscopic serial reconstruction and electron microscopy. The distal segment of preterminal portal venules (DS/PPV) with an inner diameter of 40 to 80 microm showed complete obliteration of the lumen over a 300-microm distance caused by the intense contraction of perivascular smooth muscle cells and protruding of endothelial cells into the lumen. The proximal segment of preterminal portal venules (PS/PPV) with a larger diameter up to 150 microm also underwent strong constriction, but still had luminal space for the flow, while the PS/PPV with a diameter of 150 to 400 microm showed moderate or mild constriction and retained a wide lumen. Neither terminal portal venules, inlet venules, sinusoids, nor central veins, however, exhibited demonstrable constriction. Liver parenchyma fed by the inlet venules that emerged from the PS/PPV exhibited a wide sinusoidal lumen and vacuolated hepatocytes caused by the influx of excess portal perfusate that escaped from the occlusive areas. The present study has revealed that the DS/PPV functions as a presinusoidal quasi-sphincter mechanism and is involved in the redistribution of intrahepatic portal flow under increased portal pressure.

Ultrastructural analysis of the liver with portal vein agenesis: a case report.

Congenital absence of portal vein (CAPV) is a rare vascular malformation: all 16 cases up to now reported are associated with other congenital anomalies and with benign or malignant hepatic neoplasms. Our report concerns a girl with a complex malformative syndrome consisting of CAPV, nodular tumor-like hyperplasia of the liver, and multicystic kidney dysplasia. CAPV was diagnosed by angiography, showing the splenic vein and superior mesenteric vein joined to form a "common trunk" directly entering the inferior vena cava above the liver. The liver maintained the normal lobular architecture, but immunohistochemical and ultrastructural observations revealed abnormalities of the hepatocyte membranes and diffuse capillarization of the sinusoids. In this paper, we present the relationship between the tissue modification and the lobular microcirculation changes due to CAPV, with exclusive perfusion of arterial blood flow.

Different subtypes of alpha 1A-adrenoceptor mediating contraction of rat epididymal vas deferens, rat hepatic portal vein and human prostate distinguished by the antagonist RS 17053.

1. The alpha 1-adrenoceptor subtype mediating contraction of the rat hepatic portal vein to phenylephrine was characterized by use of competitive antagonists previously shown to have selectivity between the expressed alpha 1-subtype clones. Prazosin competitively antagonized the phenylephrine contractions with a pA2 value of 9.2, as did WB 4101 (pA2 9.4), 5-methyl urapidil (pA2 8.6), indoramin (pA2 8.4) and BMY 7378 (pA2 6.5). 2. The pA2 values on the rat portal vein correlated highly with their previously published pA2 values for the alpha 1A-adrenoceptors mediating contraction of the rat epididymal vas deferens and human prostate and poorly with those for the alpha 1B- and alpha 1D-adrenoceptors mediating contraction of the rat spleen and aorta, respectively. The antagonist pA2 values on the rat portal vein correlated highly with their previously published pK1 values for the expressed alpha 1a-clone and poorly with those for the expressed alpha 1b- and alpha 1d-clones. Therefore the results show that contraction of the rat portal vein to phenylephrine is mediated by alpha 1A-adrenoceptors. 3. The novel alpha 1-adrenoceptor antagonist RS 17053 had a relatively high affinity for the alpha 1A-adrenoceptors mediating contraction of the rat epididymal vas deferens (pA2 9.5) compared with the alpha 1B-adrenoceptors in the rat spleen (pA2 7.2) or the alpha 1D-adrenoceptors in the rat aorta (pKB 7.1), in agreement with its selectivity for the expressed alpha 1a-clone. However, RS 17053 had over 100 fold lower affinity for the alpha 1A-adrenoceptors mediating contraction of the rat portal vein (pKB 7.1) and human prostate (pKB 7.1) compared with its affinity for the alpha 1A-adrenoceptors in the rat epididymal vas deferens or the expressed alpha 1a-clone. 4. The difference in affinity of RS 17053 between the rat epididymal vas deferens and rat portal vein cannot be explained by a species difference in the receptor. Therefore RS 17053 may distinguish between subtypes of the alpha 1A-adrenoceptor in the rat portal vein and human prostate compared with those in the rat epididymal vas deferens or the expressed alpha 1a-clone.

Histological changes of the liver in experimental graft-versus-host disease across minor histocompatibility barriers. VIII. Role of eosinophil infiltration.

Although eosinophil infiltrate has been recognized in hepatic graft-versus-host disease, its significance in relation to hepatic graft-versus-host disease lesions is unknown. In the present study, we analyzed hepatic eosinophil infiltration in relation to bile duct damage in experimental mouse graft-versus-host disease across minor histocompatibility barriers up to 14 months after transplantation. Portal eosinophil infiltration was found from 1 week after transplantation throughout the entire 14-month observation period. It was most striking during the early chronic stage of hepatic graft-versus-host disease between 2 to 7 months, with a peak at 5 months after transplantation. Microscopic and electron microscopic study revealed eosinophils infiltrated around the bile duct as well as in the bile duct epithelial layer. They were commonly found together with lymphocytes but were also occasionally found singly around the bile duct and in the bile duct epithelial layer. Bile duct epithelial cells in contact with and in the vicinity of eosinophils showed a variety of generative changes, occasionally associated with the presence of extracellular eosinophil granules. Bile duct epithelial cells with eosinophil infiltration just beneath the basement membrane frequently showed further characteristic severe degenerative changes with shedding or dropping-off into the lumen, which features were quite similar to those seen in the bronchial epithelium in asthma patients. These results indicate that not only lymphocytes but also eosinophils may be involved in the production of the bile duct injury in hepatic graft-versus-host disease, especially in its early chronic stage.

Vascular pattern of a metastatic liver tumor in a dog:--a scanning electron microscopic study of resin casts.

Metastasis of a malignant mixed tumor occurring in the abdominal wall was found in the liver of a 15-year-old dog male. The vascular system of the metastatic lesion was examined by scanning electron microscopy using the resin cast technique. The existence of arterio-portal shunts was confirmed. The shunts arose from branches of the hepatic artery in retrograde or vertical direction and merged into the capillary plexus replacing the branches of the portal vein, forming the so-called thread and streaks vessel in the field of hepatic angiography. Vessels with the thread and streaks appearance histologically represented tumor emboli growing in the lumen of a large branch of the portal vein. There were capillaries running inside along the portal vein and forming a longitudinal dense network in the vein. Branches of the hepatic artery feeding the metastatic lesion were well developed and formed a coarse arterial network in their course. Tributaries of the hepatic vein from the lesion were also well developed.