Portal Vein: A short thick vein formed by union of the superior mesenteric vein and the splenic vein.Hypertension, Portal: Abnormal increase of resistance to blood flow within the hepatic PORTAL SYSTEM, frequently seen in LIVER CIRRHOSIS and conditions with obstruction of the PORTAL VEIN.Portal System: A system of vessels in which blood, after passing through one capillary bed, is conveyed through a second set of capillaries before it returns to the systemic circulation. It pertains especially to the hepatic portal system.Veins: The vessels carrying blood away from the capillary beds.Mesenteric Veins: Veins which return blood from the intestines; the inferior mesenteric vein empties into the splenic vein, the superior mesenteric vein joins the splenic vein to form the portal vein.Portal Pressure: The venous pressure measured in the PORTAL VEIN.Liver Circulation: The circulation of BLOOD through the LIVER.Saphenous Vein: The vein which drains the foot and leg.Hepatic Veins: Veins which drain the liver.Varicose Veins: Enlarged and tortuous VEINS.Hepatic Artery: A branch of the celiac artery that distributes to the stomach, pancreas, duodenum, liver, gallbladder, and greater omentum.Splenic Vein: Vein formed by the union (at the hilus of the spleen) of several small veins from the stomach, pancreas, spleen and mesentery.Femoral Vein: The vein accompanying the femoral artery in the same sheath; it is a continuation of the popliteal vein and becomes the external iliac vein.Venous Thrombosis: The formation or presence of a blood clot (THROMBUS) within a vein.Portography: Examination of the portal circulation by the use of X-ray films after injection of radiopaque material.Jugular Veins: Veins in the neck which drain the brain, face, and neck into the brachiocephalic or subclavian veins.Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Portasystemic Shunt, Surgical: Surgical venous shunt between the portal and systemic circulation to effect decompression of the portal circulation. It is performed primarily in the treatment of bleeding esophageal varices resulting from portal hypertension. Types of shunt include portacaval, splenorenal, mesocaval, splenocaval, left gastric-caval (coronary-caval), portarenal, umbilicorenal, and umbilicocaval.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Renal Veins: Short thick veins which return blood from the kidneys to the vena cava.Iliac Vein: A vein on either side of the body which is formed by the union of the external and internal iliac veins and passes upward to join with its fellow of the opposite side to form the inferior vena cava.Esophageal and Gastric Varices: Dilated blood vessels in the ESOPHAGUS or GASTRIC FUNDUS that shunt blood from the portal circulation (PORTAL SYSTEM) to the systemic venous circulation. Often they are observed in individuals with portal hypertension (HYPERTENSION, PORTAL).Hepatectomy: Excision of all or part of the liver. (Dorland, 28th ed)Umbilical Veins: Venous vessels in the umbilical cord. They carry oxygenated, nutrient-rich blood from the mother to the FETUS via the PLACENTA. In humans, there is normally one umbilical vein.Portacaval Shunt, Surgical: Surgical portasystemic shunt between the portal vein and inferior vena cava.Liver Cirrhosis: Liver disease in which the normal microcirculation, the gross vascular anatomy, and the hepatic architecture have been variably destroyed and altered with fibrous septa surrounding regenerated or regenerating parenchymal nodules.Liver Neoplasms: Tumors or cancer of the LIVER.Liver Transplantation: The transference of a part of or an entire liver from one human or animal to another.Splenorenal Shunt, Surgical: Anastomosis of splenic vein to renal vein to relieve portal hypertension.Vena Cava, Inferior: The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Ligation: Application of a ligature to tie a vessel or strangulate a part.Splanchnic Circulation: The circulation of blood through the BLOOD VESSELS supplying the abdominal VISCERA.Popliteal Vein: The vein formed by the union of the anterior and posterior tibial veins; it courses through the popliteal space and becomes the femoral vein.Carcinoma, Hepatocellular: A primary malignant neoplasm of epithelial liver cells. It ranges from a well-differentiated tumor with EPITHELIAL CELLS indistinguishable from normal HEPATOCYTES to a poorly differentiated neoplasm. The cells may be uniform or markedly pleomorphic, or form GIANT CELLS. Several classification schemes have been suggested.Budd-Chiari Syndrome: A condition in which the hepatic venous outflow is obstructed anywhere from the small HEPATIC VEINS to the junction of the INFERIOR VENA CAVA and the RIGHT ATRIUM. Usually the blockage is extrahepatic and caused by blood clots (THROMBUS) or fibrous webs. Parenchymal FIBROSIS is uncommon.Subclavian Vein: The continuation of the axillary vein which follows the subclavian artery and then joins the internal jugular vein to form the brachiocephalic vein.Venous Pressure: The blood pressure in the VEINS. It is usually measured to assess the filling PRESSURE to the HEART VENTRICLE.Muscle, Smooth, Vascular: The nonstriated involuntary muscle tissue of blood vessels.Splenic Artery: The largest branch of the celiac trunk with distribution to the spleen, pancreas, stomach and greater omentum.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Gastrointestinal Hemorrhage: Bleeding in any segment of the GASTROINTESTINAL TRACT from ESOPHAGUS to RECTUM.Cerebral Veins: Veins draining the cerebrum.Portasystemic Shunt, Transjugular Intrahepatic: A type of surgical portasystemic shunt to reduce portal hypertension with associated complications of esophageal varices and ascites. It is performed percutaneously through the jugular vein and involves the creation of an intrahepatic shunt between the hepatic vein and portal vein. The channel is maintained by a metallic stent. The procedure can be performed in patients who have failed sclerotherapy and is an additional option to the surgical techniques of portocaval, mesocaval, and splenorenal shunts. It takes one to three hours to perform. (JAMA 1995;273(23):1824-30)Azygos Vein: A vein which arises from the right ascending lumbar vein or the vena cava, enters the thorax through the aortic orifice in the diaphragm, and terminates in the superior vena cava.Splenectomy: Surgical procedure involving either partial or entire removal of the spleen.Thrombosis: Formation and development of a thrombus or blood clot in the blood vessel.Phlebography: Radiographic visualization or recording of a vein after the injection of contrast medium.Anastomosis, Surgical: Surgical union or shunt between ducts, tubes or vessels. It may be end-to-end, end-to-side, side-to-end, or side-to-side.Embolization, Therapeutic: A method of hemostasis utilizing various agents such as Gelfoam, silastic, metal, glass, or plastic pellets, autologous clot, fat, and muscle as emboli. It has been used in the treatment of spinal cord and INTRACRANIAL ARTERIOVENOUS MALFORMATIONS, renal arteriovenous fistulas, gastrointestinal bleeding, epistaxis, hypersplenism, certain highly vascular tumors, traumatic rupture of blood vessels, and control of operative hemorrhage.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Liver Diseases: Pathological processes of the LIVER.Retinal Vein: Central retinal vein and its tributaries. It runs a short course within the optic nerve and then leaves and empties into the superior ophthalmic vein or cavernous sinus.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Brachiocephalic Veins: Large veins on either side of the root of the neck formed by the junction of the internal jugular and subclavian veins. They drain blood from the head, neck, and upper extremities, and unite to form the superior vena cava.Living Donors: Non-cadaveric providers of organs for transplant to related or non-related recipients.Ultrasonography, Doppler, Color: Ultrasonography applying the Doppler effect, with the superposition of flow information as colors on a gray scale in a real-time image. This type of ultrasonography is well-suited to identifying the location of high-velocity flow (such as in a stenosis) or of mapping the extent of flow in a certain region.Hypersplenism: Condition characterized by splenomegaly, some reduction in the number of circulating blood cells in the presence of a normal or hyperactive bone marrow, and the potential for reversal by splenectomy.Norepinephrine: Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.Ultrasonography, Doppler: Ultrasonography applying the Doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. (Stedman, 25th ed)Venae Cavae: The inferior and superior venae cavae.Axillary Vein: The venous trunk of the upper limb; a continuation of the basilar and brachial veins running from the lower border of the teres major muscle to the outer border of the first rib where it becomes the subclavian vein.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Angiography: Radiography of blood vessels after injection of a contrast medium.Liver Diseases, Parasitic: Liver diseases caused by infections with PARASITES, such as tapeworms (CESTODA) and flukes (TREMATODA).Retinal Vein Occlusion: Blockage of the RETINAL VEIN. Those at high risk for this condition include patients with HYPERTENSION; DIABETES MELLITUS; ATHEROSCLEROSIS; and other CARDIOVASCULAR DISEASES.Chemoembolization, Therapeutic: Administration of antineoplastic agents together with an embolizing vehicle. This allows slow release of the agent as well as obstruction of the blood supply to the neoplasm.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Constriction, Pathologic: The condition of an anatomical structure's being constricted beyond normal dimensions.Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Bile Ducts: The channels that collect and transport the bile secretion from the BILE CANALICULI, the smallest branch of the BILIARY TRACT in the LIVER, through the bile ductules, the bile ducts out the liver, and to the GALLBLADDER for storage.Liver Cirrhosis, Experimental: Experimentally induced chronic injuries to the parenchymal cells in the liver to achieve a model for LIVER CIRRHOSIS.Hepatic Encephalopathy: A syndrome characterized by central nervous system dysfunction in association with LIVER FAILURE, including portal-systemic shunts. Clinical features include lethargy and CONFUSION (frequently progressing to COMA); ASTERIXIS; NYSTAGMUS, PATHOLOGIC; brisk oculovestibular reflexes; decorticate and decerebrate posturing; MUSCLE SPASTICITY; and bilateral extensor plantar reflexes (see REFLEX, BABINSKI). ELECTROENCEPHALOGRAPHY may demonstrate triphasic waves. (From Adams et al., Principles of Neurology, 6th ed, pp1117-20; Plum & Posner, Diagnosis of Stupor and Coma, 3rd ed, p222-5)Postoperative Complications: Pathologic processes that affect patients after a surgical procedure. They may or may not be related to the disease for which the surgery was done, and they may or may not be direct results of the surgery.Liver Regeneration: Repair or renewal of hepatic tissue.Liver Function Tests: Blood tests that are used to evaluate how well a patient's liver is working and also to help diagnose liver conditions.Ascites: Accumulation or retention of free fluid within the peritoneal cavity.Liver Cirrhosis, Alcoholic: FIBROSIS of the hepatic parenchyma due to chronic excess ALCOHOL DRINKING.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Splenomegaly: Enlargement of the spleen.Sclerotherapy: Treatment of varicose veins, hemorrhoids, gastric and esophageal varices, and peptic ulcer hemorrhage by injection or infusion of chemical agents which cause localized thrombosis and eventual fibrosis and obliteration of the vessels.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.