Splenic Vein: Vein formed by the union (at the hilus of the spleen) of several small veins from the stomach, pancreas, spleen and mesentery.Portal Vein: A short thick vein formed by union of the superior mesenteric vein and the splenic vein.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.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).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.Veins: The vessels carrying blood away from the capillary beds.Splenic Artery: The largest branch of the celiac trunk with distribution to the spleen, pancreas, stomach and greater omentum.Splenic DiseasesHypersplenism: 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.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.Gastrointestinal Hemorrhage: Bleeding in any segment of the GASTROINTESTINAL TRACT from ESOPHAGUS to RECTUM.Renal Veins: Short thick veins which return blood from the kidneys to the vena cava.Splenic RuptureSplenectomy: Surgical procedure involving either partial or entire removal of the spleen.Saphenous Vein: The vein which drains the foot and leg.Venous Thrombosis: The formation or presence of a blood clot (THROMBUS) within a vein.Splenorenal Shunt, Surgical: Anastomosis of splenic vein to renal vein to relieve portal hypertension.Splenic Neoplasms: Tumors or cancer of the SPLEEN.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.Varicose Veins: Enlarged and tortuous VEINS.Splenomegaly: Enlargement of the spleen.Pancreatectomy: Surgical removal of the pancreas. (Dorland, 28th ed)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.Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Jugular Veins: Veins in the neck which drain the brain, face, and neck into the brachiocephalic or subclavian veins.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Pancreatitis: INFLAMMATION of the PANCREAS. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of CHRONIC PANCREATITIS (International Symposium on Acute Pancreatitis, Atlanta, 1992). The two most common forms of acute pancreatitis are ALCOHOLIC PANCREATITIS and gallstone pancreatitis.Endoscopy, Gastrointestinal: Endoscopic examination, therapy or surgery of the gastrointestinal tract.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.